2013-02-03 11:47:30 +00:00
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.\" Hey Emacs! This file is -*- nroff -*- source.
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.\"
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.\" Copyright (c) 2012, Vincent Weaver
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.\"
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\"
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.\" This document is based on the perf_event.h header file, the
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.\" tools/perf/design.txt file, and a lot of bitter experience.
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.\"
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.TH PERF_EVENT_OPEN 2 2013-02-04 "Linux" "Linux Programmer's Manual"
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.SH NAME
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perf_event_open \- set up performance monitoring
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.SH SYNOPSIS
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.nf
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.B #include <linux/perf_event.h>
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.B #include <linux/hw_breakpoint.h>
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.sp
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.BI "int perf_event_open(struct perf_event_attr *" attr ,
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.BI " pid_t " pid ", int " cpu ", int " group_fd ,
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.BI " unsigned long " flags );
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.fi
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.IR Note :
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There is no glibc wrapper for this system call; see NOTES.
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.SH DESCRIPTION
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Given a list of parameters,
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.BR perf_event_open ()
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returns a file descriptor, for use in subsequent system calls
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.RB ( read "(2), " mmap "(2), " prctl "(2), " fcntl "(2), etc.)."
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.PP
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A call to
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.BR perf_event_open ()
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creates a file descriptor that allows measuring performance
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information.
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Each file descriptor corresponds to one
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event that is measured; these can be grouped together
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to measure multiple events simultaneously.
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.PP
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Events can be enabled and disabled in two ways: via
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.BR ioctl (2)
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and via
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.BR prctl (2) .
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When an event is disabled it does not count or generate overflows but does
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continue to exist and maintain its count value.
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.PP
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Events come in two flavors: counting and sampled.
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A
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.I counting
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event is one that is used for counting the aggregate number of events
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that occur.
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In general, counting event results are gathered with a
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.BR read (2)
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call.
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A
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.I sampling
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event periodically writes measurements to a buffer that can then
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be accessed via
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.BR mmap (2) .
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.SS Arguments
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.P
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The argument
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.I pid
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allows events to be attached to processes in various ways.
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If
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.I pid
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is 0, measurements happen on the current thread, if
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.I pid
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is greater than 0, the process indicated by
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.I pid
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is measured, and if
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.I pid
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is \-1, all processes are counted.
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The
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.I cpu
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argument allows measurements to be specific to a CPU.
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If
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.I cpu
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is greater than or equal to 0,
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measurements are restricted to the specified CPU;
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if
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.I cpu
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is \-1, the events are measured on all CPUs.
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.P
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Note that the combination of
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.IR pid " == \-1"
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and
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.IR cpu " == \-1"
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is not valid.
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.P
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A
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.IR pid " > 0"
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and
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.IR cpu " == \-1"
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setting measures per-process and follows that process to whatever CPU the
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process gets scheduled to.
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Per-process events can be created by any user.
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.P
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A
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.IR pid " == \-1"
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and
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.IR cpu " >= 0"
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setting is per-CPU and measures all processes on the specified CPU.
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Per-CPU events need the
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.B CAP_SYS_ADMIN
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capability or a
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.I /proc/sys/kernel/perf_event_paranoid
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value of less than 1.
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.P
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The
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.I group_fd
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argument allows event groups to be created.
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An event group has one event which is the group leader.
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The leader is created first, with
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.IR group_fd " = \-1."
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The rest of the group members are created with subsequent
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.BR perf_event_open ()
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calls with
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.IR group_fd
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being set to the fd of the group leader.
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(A single event on its own is created with
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.IR group_fd " = \-1"
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and is considered to be a group with only 1 member.)
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An event group is scheduled onto the CPU as a unit: it will only
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be put onto the CPU if all of the events in the group can be put onto
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the CPU.
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This means that the values of the member events can be
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meaningfully compared, added, divided (to get ratios), etc., with each
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other, since they have counted events for the same set of executed
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instructions.
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.P
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The
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.I flags
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argument takes one of the following values:
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.TP
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.BR PERF_FLAG_FD_NO_GROUP
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.\" FIXME The following sentence is unclear
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This flag allows creating an event as part of an event group but
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having no group leader.
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It is unclear why this is useful.
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.\" FIXME So, why is it useful?
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.TP
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.BR PERF_FLAG_FD_OUTPUT
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This flag re-routes the output from an event to the group leader.
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.TP
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.BR PERF_FLAG_PID_CGROUP " (Since Linux 2.6.39)."
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This flag activates per-container system-wide monitoring.
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A container
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is an abstraction that isolates a set of resources for finer grain
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control (CPUs, memory, etc...).
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In this mode, the event is measured
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only if the thread running on the monitored CPU belongs to the designated
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container (cgroup).
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The cgroup is identified by passing a file descriptor
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opened on its directory in the cgroupfs filesystem.
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For instance, if the
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cgroup to monitor is called
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.IR test ,
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then a file descriptor opened on
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.I /dev/cgroup/test
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(assuming cgroupfs is mounted on
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.IR /dev/cgroup )
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must be passed as the
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.I pid
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parameter.
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cgroup monitoring is only available
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for system-wide events and may therefore require extra permissions.
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.P
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The
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.I perf_event_attr
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structure provides detailed configuration information
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for the event being created.
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.in +4n
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.nf
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struct perf_event_attr {
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__u32 type; /* Type of event */
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__u32 size; /* Size of attribute structure */
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__u64 config; /* Type-specific configuration */
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union {
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__u64 sample_period; /* Period of sampling */
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__u64 sample_freq; /* Frequency of sampling */
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};
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__u64 sample_type; /* Specifies values included in sample */
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__u64 read_format; /* Specifies values returned in read */
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2013-02-03 11:55:04 +00:00
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__u64 disabled : 1, /* off by default */
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inherit : 1, /* children inherit it */
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pinned : 1, /* must always be on PMU */
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exclusive : 1, /* only group on PMU */
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exclude_user : 1, /* don't count user */
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exclude_kernel : 1, /* don't count kernel */
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exclude_hv : 1, /* don't count hypervisor */
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exclude_idle : 1, /* don't count when idle */
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mmap : 1, /* include mmap data */
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comm : 1, /* include comm data */
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freq : 1, /* use freq, not period */
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inherit_stat : 1, /* per task counts */
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enable_on_exec : 1, /* next exec enables */
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task : 1, /* trace fork/exit */
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watermark : 1, /* wakeup_watermark */
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precise_ip : 2, /* skid constraint */
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mmap_data : 1, /* non-exec mmap data */
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sample_id_all : 1, /* sample_type all events */
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exclude_host : 1, /* don't count in host */
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exclude_guest : 1, /* don't count in guest */
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exclude_callchain_kernel : 1,
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/* exclude kernel callchains */
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exclude_callchain_user : 1,
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/* exclude user callchains */
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__reserved_1 : 41;
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union {
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__u32 wakeup_events; /* wakeup every n events */
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__u32 wakeup_watermark; /* bytes before wakeup */
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};
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__u32 bp_type; /* breakpoint type */
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union {
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__u64 bp_addr; /* breakpoint address */
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__u64 config1; /* extension of config */
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};
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union {
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__u64 bp_len; /* breakpoint length */
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__u64 config2; /* extension of config1 */
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};
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__u64 branch_sample_type; /* enum perf_branch_sample_type */
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__u64 sample_regs_user; /* user regs to dump on samples */
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__u32 sample_stack_user; /* size of stack to dump on
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samples */
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__u32 __reserved_2; /* Align to u64 */
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};
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.fi
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.in
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The fields of the
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.I perf_event_attr
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structure are described in more detail below:
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.TP
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.I type
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This field specifies the overall event type.
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It has one of the following values:
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.RS
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.TP
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.B PERF_TYPE_HARDWARE
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This indicates one of the "generalized" hardware events provided
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by the kernel.
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See the
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.I config
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field definition for more details.
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.TP
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.B PERF_TYPE_SOFTWARE
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This indicates one of the software-defined events provided by the kernel
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(even if no hardware support is available).
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.TP
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.B PERF_TYPE_TRACEPOINT
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This indicates a tracepoint
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provided by the kernel tracepoint infrastructure.
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.TP
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.B PERF_TYPE_HW_CACHE
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This indicates a hardware cache event.
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This has a special encoding, described in the
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.I config
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field definition.
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.TP
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.B PERF_TYPE_RAW
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This indicates a "raw" implementation-specific event in the
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.IR config " field."
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.TP
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.BR PERF_TYPE_BREAKPOINT " (Since Linux 2.6.33)"
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This indicates a hardware breakpoint as provided by the CPU.
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Breakpoints can be read/write accesses to an address as well as
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execution of an instruction address.
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.TP
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.RB "dynamic PMU"
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Since Linux 2.6.39,
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.BR perf_event_open ()
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can support multiple PMUs.
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To enable this, a value exported by the kernel can be used in the
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.I type
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field to indicate which PMU to use.
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The value to use can be found in the sysfs filesystem:
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there is a subdirectory per PMU instance under
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.IR /sys/bus/event_source/devices .
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In each sub-directory there is a
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.I type
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file whose content is an integer that can be used in the
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.I type
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field.
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For instance,
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.I /sys/bus/event_source/devices/cpu/type
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contains the value for the core CPU PMU, which is usually 4.
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.RE
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.TP
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.I "size"
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The size of the
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.I perf_event_attr
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structure for forward/backward compatibility.
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Set this using
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.I sizeof(struct perf_event_attr)
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to allow the kernel to see
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the struct size at the time of compilation.
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The related define
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.B PERF_ATTR_SIZE_VER0
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is set to 64; this was the size of the first published struct.
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.B PERF_ATTR_SIZE_VER1
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is 72, corresponding to the addition of breakpoints in Linux 2.6.33.
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.B PERF_ATTR_SIZE_VER2
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is 80 corresponding to the addition of branch sampling in Linux 3.4.
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.B PERF_ATR_SIZE_VER3
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is 96 corresponding to the addition
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of sample_regs_user and sample_stack_user in Linux 3.7.
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.TP
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.I "config"
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This specifies which event you want, in conjunction with
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the
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.I type
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field.
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The
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.IR config1 " and " config2
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fields are also taken into account in cases where 64 bits is not
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enough to fully specify the event.
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The encoding of these fields are event dependent.
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The most significant bit (bit 63) of
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.I config
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signifies CPU-specific (raw) counter configuration data;
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if the most significant bit is unset, the next 7 bits are an event
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type and the rest of the bits are the event identifier.
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There are various ways to set the
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.I config
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field that are dependent on the value of the previously
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described
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.I type
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field.
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What follows are various possible settings for
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.I config
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separated out by
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.IR type .
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If
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.I type
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is
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.BR PERF_TYPE_HARDWARE ,
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we are measuring one of the generalized hardware CPU events.
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Not all of these are available on all platforms.
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Set
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.I config
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to one of the following:
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.RS 12
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.TP
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|
.B PERF_COUNT_HW_CPU_CYCLES
|
|
|
|
Total cycles.
|
|
|
|
Be wary of what happens during CPU frequency scaling
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_INSTRUCTIONS
|
|
|
|
Retired instructions.
|
|
|
|
Be careful, these can be affected by various
|
|
|
|
issues, most notably hardware interrupt counts
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_REFERENCES
|
|
|
|
Cache accesses.
|
|
|
|
Usually this indicates Last Level Cache accesses but this may
|
|
|
|
vary depending on your CPU.
|
|
|
|
This may include prefetches and coherency messages; again this
|
|
|
|
depends on the design of your CPU.
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_MISSES
|
|
|
|
Cache misses.
|
|
|
|
Usually this indicates Last Level Cache misses; this is intended to be
|
|
|
|
used in conjunction with the
|
|
|
|
.B PERF_COUNT_HW_CACHE_REFERENCES
|
|
|
|
event to calculate cache miss rates.
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_BRANCH_INSTRUCTIONS
|
|
|
|
Retired branch instructions.
|
|
|
|
Prior to Linux 2.6.34, this used
|
|
|
|
the wrong event on AMD processors.
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_BRANCH_MISSES
|
|
|
|
Mispredicted branch instructions.
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_BUS_CYCLES
|
|
|
|
Bus cycles, which can be different from total cycles.
|
|
|
|
.TP
|
|
|
|
.BR PERF_COUNT_HW_STALLED_CYCLES_FRONTEND " (Since Linux 3.0)"
|
|
|
|
Stalled cycles during issue.
|
|
|
|
.TP
|
|
|
|
.BR PERF_COUNT_HW_STALLED_CYCLES_BACKEND " (Since Linux 3.0)"
|
|
|
|
Stalled cycles during retirement.
|
|
|
|
.TP
|
|
|
|
.BR PERF_COUNT_HW_REF_CPU_CYCLES " (Since Linux 3.3)"
|
|
|
|
Total cycles; not affected by CPU frequency scaling.
|
|
|
|
.RE
|
|
|
|
.IP
|
|
|
|
If
|
|
|
|
.I type
|
|
|
|
is
|
|
|
|
.BR PERF_TYPE_SOFTWARE ,
|
|
|
|
we are measuring software events provided by the kernel.
|
|
|
|
Set
|
|
|
|
.I config
|
|
|
|
to one of the following:
|
|
|
|
.RS 12
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_SW_CPU_CLOCK
|
|
|
|
This reports the CPU clock, a high-resolution per-CPU timer.
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_SW_TASK_CLOCK
|
|
|
|
This reports a clock count specific to the task that is running.
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_SW_PAGE_FAULTS
|
|
|
|
This reports the number of page faults.
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_SW_CONTEXT_SWITCHES
|
|
|
|
This counts context switches.
|
|
|
|
Until Linux 2.6.34, these were all reported as user-space
|
|
|
|
events, after that they are reported as happening in the kernel.
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_SW_CPU_MIGRATIONS
|
|
|
|
This reports the number of times the process
|
|
|
|
has migrated to a new CPU.
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_SW_PAGE_FAULTS_MIN
|
|
|
|
This counts the number of minor page faults.
|
|
|
|
These did not require disk I/O to handle.
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_SW_PAGE_FAULTS_MAJ
|
|
|
|
This counts the number of major page faults.
|
|
|
|
These required disk I/O to handle.
|
|
|
|
.TP
|
|
|
|
.BR PERF_COUNT_SW_ALIGNMENT_FAULTS " (Since Linux 2.6.33)"
|
|
|
|
This counts the number of alignment faults.
|
|
|
|
These happen when unaligned memory accesses happen; the kernel
|
|
|
|
can handle these but it reduces performance.
|
|
|
|
This only happens on some architectures (never on x86).
|
|
|
|
.TP
|
|
|
|
.BR PERF_COUNT_SW_EMULATION_FAULTS " (Since Linux 2.6.33)"
|
|
|
|
This counts the number of emulation faults.
|
|
|
|
The kernel sometimes traps on unimplemented instructions
|
2013-02-03 11:55:04 +00:00
|
|
|
and emulates them for user space.
|
2013-02-03 11:47:30 +00:00
|
|
|
This can negatively impact performance.
|
|
|
|
.RE
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.RS
|
|
|
|
If
|
|
|
|
.I type
|
|
|
|
is
|
|
|
|
.BR PERF_TYPE_TRACEPOINT ,
|
|
|
|
then we are measuring kernel tracepoints.
|
|
|
|
The value to use in
|
|
|
|
.I config
|
|
|
|
can be obtained from under debugfs
|
|
|
|
.I tracing/events/*/*/id
|
|
|
|
if ftrace is enabled in the kernel.
|
|
|
|
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.RS
|
|
|
|
If
|
|
|
|
.I type
|
|
|
|
is
|
|
|
|
.BR PERF_TYPE_HW_CACHE ,
|
|
|
|
then we are measuring a hardware CPU cache event.
|
|
|
|
To calculate the appropriate
|
|
|
|
.I config
|
|
|
|
value use the following equation:
|
|
|
|
.RS 4
|
|
|
|
.nf
|
|
|
|
|
|
|
|
(perf_hw_cache_id) | (perf_hw_cache_op_id << 8) |
|
|
|
|
(perf_hw_cache_op_result_id << 16)
|
|
|
|
.fi
|
|
|
|
.P
|
|
|
|
where
|
|
|
|
.I perf_hw_cache_id
|
|
|
|
is one of:
|
2013-02-03 11:55:04 +00:00
|
|
|
.RS 4
|
2013-02-03 11:47:30 +00:00
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_L1D
|
|
|
|
for measuring Level 1 Data Cache
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_L1I
|
|
|
|
for measuring Level 1 Instruction Cache
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_LL
|
|
|
|
for measuring Last-Level Cache
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_DTLB
|
|
|
|
for measuring the Data TLB
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_ITLB
|
|
|
|
for measuring the Instruction TLB
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_BPU
|
|
|
|
for measuring the branch prediction unit
|
|
|
|
.TP
|
|
|
|
.BR PERF_COUNT_HW_CACHE_NODE " (Since Linux 3.0)"
|
|
|
|
for measuring local memory accesses
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.P
|
|
|
|
and
|
|
|
|
.I perf_hw_cache_op_id
|
|
|
|
is one of
|
2013-02-03 11:55:04 +00:00
|
|
|
.RS 4
|
2013-02-03 11:47:30 +00:00
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_OP_READ
|
|
|
|
for read accesses
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_OP_WRITE
|
|
|
|
for write accesses
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_OP_PREFETCH
|
|
|
|
for prefetch accesses
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.P
|
|
|
|
and
|
|
|
|
.I perf_hw_cache_op_result_id
|
|
|
|
is one of
|
2013-02-03 11:55:04 +00:00
|
|
|
.RS 4
|
2013-02-03 11:47:30 +00:00
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_RESULT_ACCESS
|
|
|
|
to measure accesses
|
|
|
|
.TP
|
|
|
|
.B PERF_COUNT_HW_CACHE_RESULT_MISS
|
|
|
|
to measure misses
|
|
|
|
.RE
|
|
|
|
.RE
|
|
|
|
|
|
|
|
If
|
|
|
|
.I type
|
|
|
|
is
|
|
|
|
.BR PERF_TYPE_RAW ,
|
|
|
|
then a custom "raw"
|
|
|
|
.I config
|
|
|
|
value is needed.
|
|
|
|
Most CPUs support events that are not covered by the "generalized" events.
|
|
|
|
These are implementation defined; see your CPU manual (for example
|
|
|
|
the Intel Volume 3B documentation or the AMD BIOS and Kernel Developer
|
|
|
|
Guide).
|
|
|
|
The libpfm4 library can be used to translate from the name in the
|
|
|
|
architectural manuals to the raw hex value
|
|
|
|
.BR perf_event_open ()
|
|
|
|
expects in this field.
|
|
|
|
|
|
|
|
If
|
|
|
|
.I type
|
|
|
|
is
|
|
|
|
.BR PERF_TYPE_BREAKPOINT ,
|
|
|
|
then leave
|
|
|
|
.I config
|
|
|
|
set to zero.
|
|
|
|
Its parameters are set in other places.
|
|
|
|
.RE
|
|
|
|
.TP
|
|
|
|
.IR sample_period ", " sample_freq
|
|
|
|
A "sampling" counter is one that generates an interrupt
|
|
|
|
every N events, where N is given by
|
|
|
|
.IR sample_period .
|
|
|
|
A sampling counter has
|
|
|
|
.IR sample_period " > 0."
|
|
|
|
When an overflow interrupt occurs, requested data is recorded
|
|
|
|
in the mmap buffer.
|
|
|
|
The
|
|
|
|
.I sample_type
|
|
|
|
field controls what data is recorded on each interrupt.
|
|
|
|
|
|
|
|
.I sample_freq
|
|
|
|
can be used if you wish to use frequency rather than period.
|
|
|
|
In this case you set the
|
|
|
|
.I freq
|
|
|
|
flag.
|
|
|
|
The kernel will adjust the sampling period
|
|
|
|
to try and achieve the desired rate.
|
|
|
|
The rate of adjustment is a
|
|
|
|
timer tick.
|
|
|
|
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I "sample_type"
|
|
|
|
The various bits in this field specify which values to include
|
|
|
|
in the sample.
|
|
|
|
They will be recorded in a ring-buffer,
|
|
|
|
which is available to user-space using
|
|
|
|
.BR mmap (2).
|
|
|
|
The order in which the values are saved in the
|
|
|
|
sample are documented in the MMAP Layout subsection below;
|
|
|
|
it is not the
|
|
|
|
.I "enum perf_event_sample_format"
|
|
|
|
order.
|
|
|
|
.RS
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_IP
|
|
|
|
Records instruction pointer.
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_TID
|
2013-02-03 11:55:04 +00:00
|
|
|
Records the process and thread IDs.
|
2013-02-03 11:47:30 +00:00
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_TIME
|
|
|
|
Records a timestamp.
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_ADDR
|
|
|
|
Records an address, if applicable.
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_READ
|
|
|
|
Record counter values for all events in a group, not just the group leader.
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_CALLCHAIN
|
|
|
|
Records the callchain (stack backtrace).
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_ID
|
|
|
|
Records a unique ID for the opened event's group leader.
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_CPU
|
|
|
|
Records CPU number.
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_PERIOD
|
|
|
|
Records the current sampling period.
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_STREAM_ID
|
|
|
|
Records a unique ID for the opened event.
|
|
|
|
Unlike
|
|
|
|
.B PERF_SAMPLE_ID
|
|
|
|
the actual ID is returned, not the group leader.
|
|
|
|
This ID is the same as the one returned by PERF_FORMAT_ID.
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_RAW
|
|
|
|
Records additional data, if applicable.
|
|
|
|
Usually returned by tracepoint events.
|
|
|
|
.TP
|
|
|
|
.BR PERF_SAMPLE_BRANCH_STACK " (Since Linux 3.4)"
|
2013-02-03 11:55:04 +00:00
|
|
|
Records the branch stack.
|
|
|
|
See branch_sample_type.
|
2013-02-03 11:47:30 +00:00
|
|
|
.TP
|
|
|
|
.BR PERF_SAMPLE_REGS_USER " (Since Linux 3.7)"
|
|
|
|
Records the current register state.
|
|
|
|
.TP
|
|
|
|
.BR PERF_SAMPLE_STACK_USER " (Since Linux 3.7)"
|
|
|
|
[To be documented]
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "read_format"
|
|
|
|
This field specifies the format of the data returned by
|
|
|
|
.BR read (2)
|
|
|
|
on a
|
2013-02-03 11:55:04 +00:00
|
|
|
.BR perf_event_open ()
|
2013-02-03 11:47:30 +00:00
|
|
|
file descriptor.
|
|
|
|
.RS
|
|
|
|
.TP
|
|
|
|
.B PERF_FORMAT_TOTAL_TIME_ENABLED
|
|
|
|
Adds the 64-bit "time_enabled" field.
|
|
|
|
This can be used to calculate estimated totals if
|
|
|
|
the PMU is overcommitted and multiplexing is happening.
|
|
|
|
.TP
|
|
|
|
.B PERF_FORMAT_TOTAL_TIME_RUNNING
|
|
|
|
Adds the 64-bit "time_running" field.
|
|
|
|
This can be used to calculate estimated totals if
|
|
|
|
the PMU is overcommitted and multiplexing is happening.
|
|
|
|
.TP
|
|
|
|
.B PERF_FORMAT_ID
|
|
|
|
Adds a 64-bit unique value that corresponds to the event group.
|
|
|
|
.TP
|
|
|
|
.B PERF_FORMAT_GROUP
|
|
|
|
Allows all counter values in an event group to be read with one read.
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "disabled"
|
|
|
|
The
|
|
|
|
.I disabled
|
|
|
|
bit specifies whether the counter starts out disabled or enabled.
|
|
|
|
If disabled, the event can later be enabled by
|
|
|
|
.BR ioctl (2),
|
|
|
|
.BR prctl (2),
|
|
|
|
or
|
|
|
|
.IR enable_on_exec .
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "inherit"
|
|
|
|
The
|
|
|
|
.I inherit
|
|
|
|
bit specifies that this counter should count events of child
|
|
|
|
tasks as well as the task specified.
|
|
|
|
This only applies to new children, not to any existing children at
|
|
|
|
the time the counter is created (nor to any new children of
|
|
|
|
existing children).
|
|
|
|
|
|
|
|
Inherit does not work for some combinations of
|
|
|
|
.IR read_format s,
|
|
|
|
such as
|
|
|
|
.BR PERF_FORMAT_GROUP .
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "pinned"
|
|
|
|
The
|
|
|
|
.I pinned
|
|
|
|
bit specifies that the counter should always be on the CPU if at all
|
|
|
|
possible.
|
|
|
|
It only applies to hardware counters and only to group leaders.
|
|
|
|
If a pinned counter cannot be put onto the CPU (e.g., because there are
|
|
|
|
not enough hardware counters or because of a conflict with some other
|
|
|
|
event), then the counter goes into an 'error' state, where reads
|
|
|
|
return end-of-file (i.e.,
|
|
|
|
.BR read (2)
|
|
|
|
returns 0) until the counter is subsequently enabled or disabled.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "exclusive"
|
|
|
|
The
|
|
|
|
.I exclusive
|
|
|
|
bit specifies that when this counter's group is on the CPU,
|
|
|
|
it should be the only group using the CPU's counters.
|
|
|
|
In the future this may allow monitoring programs to
|
|
|
|
support PMU features that need to run alone so that they do not
|
|
|
|
disrupt other hardware counters.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "exclude_user"
|
|
|
|
If this bit is set, the count excludes events that happen in user-space.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "exclude_kernel"
|
|
|
|
If this bit is set, the count excludes events that happen in kernel-space.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "exclude_hv"
|
|
|
|
If this bit is set, the count excludes events that happen in the
|
|
|
|
hypervisor.
|
|
|
|
This is mainly for PMUs that have built-in support for handling this
|
|
|
|
(such as POWER).
|
|
|
|
Extra support is needed for handling hypervisor measurements on most
|
|
|
|
machines.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "exclude_idle"
|
|
|
|
If set, don't count when the CPU is idle.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "mmap"
|
|
|
|
The
|
|
|
|
.I mmap
|
|
|
|
bit enables recording of exec mmap events.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "comm"
|
|
|
|
The
|
|
|
|
.I comm
|
|
|
|
bit enables tracking of process command name as modified by the
|
|
|
|
.IR exec (2)
|
|
|
|
and
|
|
|
|
.IR prctl (PR_SET_NAME)
|
|
|
|
system calls.
|
|
|
|
Unfortunately for tools,
|
|
|
|
there is no way to distinguish one system call versus the other.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "freq"
|
|
|
|
If this bit is set, then
|
|
|
|
.I sample_frequency
|
|
|
|
not
|
|
|
|
.I sample_period
|
|
|
|
is used when setting up the sampling interval.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "inherit_stat"
|
|
|
|
This bit enables saving of event counts on context switch for
|
|
|
|
inherited tasks.
|
|
|
|
This is only meaningful if the
|
|
|
|
.I inherit
|
|
|
|
field is set.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "enable_on_exec"
|
|
|
|
If this bit is set, a counter is automatically
|
|
|
|
enabled after a call to
|
|
|
|
.BR exec (2).
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "task"
|
|
|
|
If this bit is set, then
|
|
|
|
fork/exit notifications are included in the ring buffer.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "watermark"
|
|
|
|
If set, have a sampling interrupt happen when we cross the
|
|
|
|
.I wakeup_watermark
|
|
|
|
boundary.
|
|
|
|
Otherwise interrupts happen after
|
|
|
|
.I wakeup_events
|
|
|
|
samples.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "precise_ip" " (Since Linux 2.6.35)"
|
|
|
|
This controls the amount of skid.
|
|
|
|
Skid is how many instructions
|
|
|
|
execute between an event of interest happening and the kernel
|
|
|
|
being able to stop and record the event.
|
|
|
|
Smaller skid is
|
|
|
|
better and allows more accurate reporting of which events
|
|
|
|
correspond to which instructions, but hardware is often limited
|
|
|
|
with how small this can be.
|
|
|
|
|
|
|
|
The values of this are the following:
|
|
|
|
.RS
|
|
|
|
.TP
|
|
|
|
0 -
|
|
|
|
.B SAMPLE_IP
|
|
|
|
can have arbitrary skid
|
|
|
|
.TP
|
|
|
|
1 -
|
|
|
|
.B SAMPLE_IP
|
|
|
|
must have constant skid
|
|
|
|
.TP
|
|
|
|
2 -
|
|
|
|
.B SAMPLE_IP
|
|
|
|
requested to have 0 skid
|
|
|
|
.TP
|
|
|
|
3 -
|
|
|
|
.B SAMPLE_IP
|
|
|
|
must have 0 skid.
|
|
|
|
See also
|
|
|
|
.BR PERF_RECORD_MISC_EXACT_IP .
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "mmap_data" " (Since Linux 2.6.36)"
|
|
|
|
The counterpart of the
|
|
|
|
.I mmap
|
|
|
|
field, but enables including data mmap events
|
|
|
|
in the ring-buffer.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "sample_id_all" " (Since Linux 2.6.38)"
|
|
|
|
If set, then TID, TIME, ID, CPU, and STREAM_ID can
|
|
|
|
additionally be included in
|
|
|
|
.RB non- PERF_RECORD_SAMPLE s
|
|
|
|
if the corresponding
|
|
|
|
.I sample_type
|
|
|
|
is selected.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "exclude_host" " (Since Linux 3.2)"
|
|
|
|
Do not measure time spent in VM host
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "exclude_guest" " (Since Linux 3.2)"
|
|
|
|
Do not measure time spent in VM guest
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "exclude_callchain_kernel" " (Since Linux 3.7)"
|
|
|
|
Do not include kernel callchains.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "exclude_callchain_user" " (Since Linux 3.7)"
|
|
|
|
Do not include user callchains.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "wakeup_events" ", " "wakeup_watermark"
|
|
|
|
This union sets how many samples
|
|
|
|
.RI ( wakeup_events )
|
|
|
|
or bytes
|
|
|
|
.RI ( wakeup_watermark )
|
|
|
|
happen before an overflow signal happens.
|
|
|
|
Which one is used is selected by the
|
|
|
|
.I watermark
|
|
|
|
bitflag.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "bp_type" " (Since Linux 2.6.33)"
|
|
|
|
This chooses the breakpoint type.
|
|
|
|
It is one of:
|
|
|
|
.RS
|
|
|
|
.TP
|
|
|
|
.BR HW_BREAKPOINT_EMPTY
|
|
|
|
no breakpoint
|
|
|
|
.TP
|
|
|
|
.BR HW_BREAKPOINT_R
|
|
|
|
count when we read the memory location
|
|
|
|
.TP
|
|
|
|
.BR HW_BREAKPOINT_W
|
|
|
|
count when we write the memory location
|
|
|
|
.TP
|
|
|
|
.BR HW_BREAKPOINT_RW
|
|
|
|
count when we read or write the memory location
|
|
|
|
.TP
|
|
|
|
.BR HW_BREAKPOINT_X
|
|
|
|
count when we execute code at the memory location
|
|
|
|
|
|
|
|
.LP
|
2013-02-03 11:55:04 +00:00
|
|
|
The values can be combined via a bitwise or, but the
|
2013-02-03 11:47:30 +00:00
|
|
|
combination of
|
|
|
|
.B HW_BREAKPOINT_R
|
|
|
|
or
|
|
|
|
.B HW_BREAKPOINT_W
|
|
|
|
with
|
|
|
|
.B HW_BREAKPOINT_X
|
|
|
|
is not allowed.
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "bp_addr" " (Since Linux 2.6.33)"
|
|
|
|
.I bp_addr
|
|
|
|
address of the breakpoint.
|
|
|
|
For execution breakpoints this is the memory address of the instruction
|
|
|
|
of interest; for read and write breakpoints it is the memory address
|
|
|
|
of the memory location of interest.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "config1" " (Since Linux 2.6.39)"
|
|
|
|
.I config1
|
|
|
|
is used for setting events that need an extra register or otherwise
|
|
|
|
do not fit in the regular config field.
|
|
|
|
Raw OFFCORE_EVENTS on Nehalem/Westmere/SandyBridge use this field
|
|
|
|
on 3.3 and later kernels.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "bp_len" " (Since Linux 2.6.33)"
|
|
|
|
.I bp_len
|
|
|
|
is the length of the breakpoint being measured if
|
|
|
|
.I type
|
|
|
|
is
|
|
|
|
.BR PERF_TYPE_BREAKPOINT .
|
|
|
|
Options are
|
|
|
|
.BR HW_BREAKPOINT_LEN_1 ,
|
|
|
|
.BR HW_BREAKPOINT_LEN_2 ,
|
|
|
|
.BR HW_BREAKPOINT_LEN_4 ,
|
|
|
|
.BR HW_BREAKPOINT_LEN_8 .
|
|
|
|
For an execution breakpoint, set this to
|
|
|
|
.IR sizeof(long) .
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "config2" " (Since Linux 2.6.39)"
|
|
|
|
|
|
|
|
.I config2
|
|
|
|
is a further extension of the
|
|
|
|
.I config1
|
|
|
|
field.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "branch_sample_type" " (Since Linux 3.4)"
|
|
|
|
This is used with the CPUs hardware branch sampling, if available.
|
|
|
|
It can have one of the following values:
|
|
|
|
.RS
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_BRANCH_USER
|
|
|
|
Branch target is in user space
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_BRANCH_KERNEL
|
|
|
|
Branch target is in kernel space
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_BRANCH_HV
|
|
|
|
Branch target is in hypervisor
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_BRANCH_ANY
|
|
|
|
Any branch type.
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_BRANCH_ANY_CALL
|
|
|
|
Any call branch
|
|
|
|
.TP
|
|
|
|
.B PERF_SAMPLE_BRANCH_ANY_RETURN
|
|
|
|
Any return branch
|
|
|
|
.TP
|
|
|
|
.BR PERF_SAMPLE_BRANCH_IND_CALL
|
|
|
|
Indirect calls
|
|
|
|
.TP
|
|
|
|
.BR PERF_SAMPLE_BRANCH_PLM_ALL
|
|
|
|
User, kernel, and hv
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "sample_regs_user" " (Since Linux 3.7)"
|
|
|
|
This defines the set of user registers to dump on samples.
|
2013-02-03 11:55:04 +00:00
|
|
|
See
|
2013-02-24 14:26:04 +00:00
|
|
|
.\" FIXME: The following reference seems to be not quite right:
|
2013-02-03 11:55:04 +00:00
|
|
|
.IR asm/perf_regs.h .
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR "sample_stack_user" " (Since Linux 3.7)"
|
|
|
|
This defines the size of the user stack to dump on sample.
|
|
|
|
|
|
|
|
.RE
|
|
|
|
|
intro.1, time.1, _syscall.2, accept.2, brk.2, capget.2, faccessat.2, futimesat.2, gethostname.2, intro.2, ioprio_set.2, kill.2, madvise.2, mlock.2, mount.2, msgget.2, perf_event_open.2, poll.2, readv.2, sched_rr_get_interval.2, sched_setscheduler.2, select.2, select_tut.2, shmget.2, stat.2, timer_create.2, ustat.2, vfork.2, wait.2, alloca.3, atexit.3, catopen.3, crypt.3, dbopen.3, fenv.3, fopen.3, getaddrinfo_a.3, gethostbyname.3, getutent.3, intro.3, login.3, mallopt.3, queue.3, regex.3, sigpause.3, sigsetops.3, stdio.3, strftime.3, strptime.3, sysconf.3, ttyslot.3, undocumented.3, cciss.4, console_codes.4, hpsa.4, initrd.4, intro.4, rtc.4, st.4, tty_ioctl.4, wavelan.4, acct.5, charmap.5, dir_colors.5, hosts.5, intro.5, termcap.5, utmp.5, intro.6, armscii-8.7, boot.7, bootparam.7, capabilities.7, cpuset.7, credentials.7, ddp.7, epoll.7, glob.7, intro.7, ip.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, man-pages.7, man.7, math_error.7, netlink.7, numa.7, packet.7, path_resolution.7, pipe.7, pthreads.7, raw.7, rtnetlink.7, signal.7, socket.7, spufs.7, svipc.7, tcp.7, time.7, udp.7, udplite.7, unicode.7, unix.7, uri.7, utf-8.7, x25.7, intro.8: Global fix: use consistent capitalization in .SS headings
Capitalization in .SS sections across pages (and sometimes even
within a single page) is wildly inconsistent. Make it consistent.
Capitalize first word in heading, but otherwise use lower case,
except where English usage (e.g., proper nouns) or programming
language requirements (e.g., identifier names) dictate otherwise.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 14:08:38 +00:00
|
|
|
.SS "Reading results"
|
2013-02-03 11:47:30 +00:00
|
|
|
Once a
|
2013-02-03 11:55:04 +00:00
|
|
|
.BR perf_event_open ()
|
2013-02-03 11:47:30 +00:00
|
|
|
file descriptor has been opened, the values
|
|
|
|
of the events can be read from the file descriptor.
|
|
|
|
The values that are there are specified by the
|
|
|
|
.I read_format
|
2013-02-03 11:55:04 +00:00
|
|
|
field in the
|
|
|
|
.I attr
|
|
|
|
structure at open time.
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
If you attempt to read into a buffer that is not big enough to hold the
|
|
|
|
data
|
|
|
|
.B ENOSPC
|
|
|
|
is returned
|
|
|
|
|
|
|
|
Here is the layout of the data returned by a read:
|
|
|
|
|
|
|
|
If
|
|
|
|
.B PERF_FORMAT_GROUP
|
|
|
|
was specified to allow reading all events in a group at once:
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct read_format {
|
|
|
|
u64 nr; /* The number of events */
|
|
|
|
u64 time_enabled; /* if PERF_FORMAT_TOTAL_TIME_ENABLED */
|
|
|
|
u64 time_running; /* if PERF_FORMAT_TOTAL_TIME_RUNNING */
|
|
|
|
struct {
|
|
|
|
u64 value; /* The value of the event */
|
|
|
|
u64 id; /* if PERF_FORMAT_ID */
|
|
|
|
} values[nr];
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
.in
|
|
|
|
|
|
|
|
If
|
|
|
|
.B PERF_FORMAT_GROUP
|
|
|
|
was
|
|
|
|
.I not
|
|
|
|
specified, then the read values look as following:
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct read_format {
|
|
|
|
u64 value; /* The value of the event */
|
|
|
|
u64 time_enabled; /* if PERF_FORMAT_TOTAL_TIME_ENABLED */
|
|
|
|
u64 time_running; /* if PERF_FORMAT_TOTAL_TIME_RUNNING */
|
|
|
|
u64 id; /* if PERF_FORMAT_ID */
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
.in
|
|
|
|
|
|
|
|
The values read are described in more detail below.
|
|
|
|
.RS
|
|
|
|
.TP
|
|
|
|
.I nr
|
|
|
|
The number of events in this file descriptor.
|
|
|
|
Only available if
|
|
|
|
.B PERF_FORMAT_GROUP
|
|
|
|
was specified.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.IR time_enabled ", " time_running
|
|
|
|
Total time the event was enabled and running.
|
|
|
|
Normally these are the same.
|
|
|
|
If more events are started
|
|
|
|
than available counter slots on the PMU, then multiplexing
|
|
|
|
happens and events only run part of the time.
|
|
|
|
In that case the
|
|
|
|
.I time_enabled
|
|
|
|
and
|
|
|
|
.I time running
|
|
|
|
values can be used to scale an estimated value for the count.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I value
|
|
|
|
An unsigned 64-bit value containing the counter result.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I id
|
|
|
|
A globally unique value for this particular event, only there if
|
|
|
|
.B PERF_FORMAT_ID
|
|
|
|
was specified in read_format.
|
|
|
|
|
|
|
|
.RE
|
|
|
|
.RE
|
|
|
|
|
|
|
|
|
|
|
|
|
intro.1, time.1, _syscall.2, accept.2, brk.2, capget.2, faccessat.2, futimesat.2, gethostname.2, intro.2, ioprio_set.2, kill.2, madvise.2, mlock.2, mount.2, msgget.2, perf_event_open.2, poll.2, readv.2, sched_rr_get_interval.2, sched_setscheduler.2, select.2, select_tut.2, shmget.2, stat.2, timer_create.2, ustat.2, vfork.2, wait.2, alloca.3, atexit.3, catopen.3, crypt.3, dbopen.3, fenv.3, fopen.3, getaddrinfo_a.3, gethostbyname.3, getutent.3, intro.3, login.3, mallopt.3, queue.3, regex.3, sigpause.3, sigsetops.3, stdio.3, strftime.3, strptime.3, sysconf.3, ttyslot.3, undocumented.3, cciss.4, console_codes.4, hpsa.4, initrd.4, intro.4, rtc.4, st.4, tty_ioctl.4, wavelan.4, acct.5, charmap.5, dir_colors.5, hosts.5, intro.5, termcap.5, utmp.5, intro.6, armscii-8.7, boot.7, bootparam.7, capabilities.7, cpuset.7, credentials.7, ddp.7, epoll.7, glob.7, intro.7, ip.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, man-pages.7, man.7, math_error.7, netlink.7, numa.7, packet.7, path_resolution.7, pipe.7, pthreads.7, raw.7, rtnetlink.7, signal.7, socket.7, spufs.7, svipc.7, tcp.7, time.7, udp.7, udplite.7, unicode.7, unix.7, uri.7, utf-8.7, x25.7, intro.8: Global fix: use consistent capitalization in .SS headings
Capitalization in .SS sections across pages (and sometimes even
within a single page) is wildly inconsistent. Make it consistent.
Capitalize first word in heading, but otherwise use lower case,
except where English usage (e.g., proper nouns) or programming
language requirements (e.g., identifier names) dictate otherwise.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 14:08:38 +00:00
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.SS "MMAP layout"
|
2013-02-03 11:47:30 +00:00
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When using
|
2013-02-03 11:55:04 +00:00
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.BR perf_event_open ()
|
2013-02-03 11:47:30 +00:00
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in sampled mode, asynchronous events
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(like counter overflow or
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.B PROT_EXEC
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mmap tracking)
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are logged into a ring-buffer.
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This ring-buffer is created and accessed through
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.BR mmap (2).
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The mmap size should be 1+2^n pages, where the first page is a
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metadata page
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.IR ( "struct perf_event_mmap_page" )
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that contains various
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bits of information such as where the ring-buffer head is.
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Before kernel 2.6.39, there is a bug that means you must allocate a mmap
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ring buffer when sampling even if you do not plan to access it.
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The structure of the first metadata mmap page is as follows:
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.in +4n
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.nf
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struct perf_event_mmap_page {
|
2013-02-03 11:55:04 +00:00
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__u32 version; /* version number of this structure */
|
2013-02-03 11:47:30 +00:00
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__u32 compat_version; /* lowest version this is compat with */
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2013-02-03 11:55:04 +00:00
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__u32 lock; /* seqlock for synchronization */
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__u32 index; /* hardware counter identifier */
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__s64 offset; /* add to hardware counter value */
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__u64 time_enabled; /* time event active */
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__u64 time_running; /* time event on CPU */
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2013-02-03 11:47:30 +00:00
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union {
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__u64 capabilities;
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__u64 cap_usr_time : 1,
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cap_usr_rdpmc : 1,
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};
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__u16 pmc_width;
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__u16 time_shift;
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__u32 time_mult;
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__u64 time_offset;
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2013-02-03 11:55:04 +00:00
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__u64 __reserved[120]; /* Pad to 1k */
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2013-02-03 11:47:30 +00:00
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__u64 data_head; /* head in the data section */
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2013-02-03 11:55:04 +00:00
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__u64 data_tail; /* user-space written tail */
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2013-02-03 11:47:30 +00:00
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}
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.fi
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.in
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The following looks at the fields in the
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.I perf_event_mmap_page
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structure in more detail.
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2013-02-03 11:55:04 +00:00
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.RS 4
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2013-02-03 11:47:30 +00:00
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.TP
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.I version
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Version number of this structure.
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.TP
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.I compat_version
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The lowest version this is compatible with.
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.TP
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.I lock
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A seqlock for synchronization.
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.TP
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.I index
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A unique hardware counter identifier.
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.TP
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.I offset
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.\" FIXME clarify
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Add this to hardware counter value??
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.TP
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.I time_enabled
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Time the event was active.
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.TP
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.I time_running
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Time the event was running.
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.TP
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.I cap_usr_time
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User time capability
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.TP
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.I cap_usr_rdpmc
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If the hardware supports user-space read of performance counters
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without syscall (this is the "rdpmc" instruction on x86), then
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the following code can be used to do a read:
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.in +4n
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.nf
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u32 seq, time_mult, time_shift, idx, width;
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u64 count, enabled, running;
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u64 cyc, time_offset;
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s64 pmc = 0;
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do {
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seq = pc\->lock;
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barrier();
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|
enabled = pc\->time_enabled;
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running = pc\->time_running;
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if (pc\->cap_usr_time && enabled != running) {
|
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cyc = rdtsc();
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time_offset = pc\->time_offset;
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time_mult = pc\->time_mult;
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|
time_shift = pc\->time_shift;
|
|
|
|
}
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idx = pc\->index;
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count = pc\->offset;
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if (pc\->cap_usr_rdpmc && idx) {
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width = pc\->pmc_width;
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|
pmc = rdpmc(idx \- 1);
|
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|
}
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|
|
barrier();
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|
} while (pc\->lock != seq);
|
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|
.fi
|
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|
.in
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.TP
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.I pmc_width
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If
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.IR cap_usr_rdpmc ,
|
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|
this field provides the bit-width of the value
|
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|
read using the rdpmc or equivalent instruction.
|
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|
|
This can be used to sign extend the result like:
|
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|
.in +4n
|
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|
.nf
|
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|
pmc <<= 64 \- pmc_width;
|
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|
pmc >>= 64 \- pmc_width; // signed shift right
|
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|
count += pmc;
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|
.fi
|
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|
.in
|
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.TP
|
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|
.IR time_shift ", " time_mult ", " time_offset
|
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|
If
|
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|
.IR cap_usr_time ,
|
|
|
|
these fields can be used to compute the time
|
2013-02-03 11:55:04 +00:00
|
|
|
delta since time_enabled (in nanoseconds) using rdtsc or similar.
|
2013-02-03 11:47:30 +00:00
|
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|
.nf
|
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|
|
u64 quot, rem;
|
|
|
|
u64 delta;
|
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|
|
quot = (cyc >> time_shift);
|
|
|
|
rem = cyc & ((1 << time_shift) \- 1);
|
|
|
|
delta = time_offset + quot * time_mult +
|
|
|
|
((rem * time_mult) >> time_shift);
|
|
|
|
.fi
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
Where
|
|
|
|
.IR time_offset ,
|
|
|
|
.IR time_mult ,
|
|
|
|
.IR time_shift ,
|
|
|
|
and
|
|
|
|
.IR cyc
|
|
|
|
are read in the
|
2013-02-03 11:47:30 +00:00
|
|
|
seqcount loop described above.
|
|
|
|
This delta can then be added to
|
|
|
|
enabled and possible running (if idx), improving the scaling:
|
|
|
|
.nf
|
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|
|
enabled += delta;
|
|
|
|
if (idx)
|
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|
|
running += delta;
|
|
|
|
quot = count / running;
|
|
|
|
rem = count % running;
|
|
|
|
count = quot * enabled + (rem * enabled) / running;
|
|
|
|
.fi
|
|
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|
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|
|
|
.TP
|
|
|
|
.I data_head
|
|
|
|
This points to the head of the data section.
|
2013-02-03 11:55:04 +00:00
|
|
|
The value continuously increases, it does not wrap.
|
|
|
|
The value needs to be manually wrapped by the size of the mmap buffer
|
2013-02-03 11:47:30 +00:00
|
|
|
before accessing the samples.
|
|
|
|
|
|
|
|
On SMP-capable platforms, after reading the data_head value,
|
|
|
|
user-space should issue an rmb().
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I data_tail;
|
|
|
|
When the mapping is
|
|
|
|
.BR PROT_WRITE ,
|
2013-02-03 11:55:04 +00:00
|
|
|
the
|
|
|
|
.I data_tail
|
|
|
|
value should be written by user space to reflect the last read data.
|
2013-02-03 11:47:30 +00:00
|
|
|
In this case the kernel will not over-write unread data.
|
|
|
|
|
|
|
|
.RE
|
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|
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|
|
|
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|
|
The following 2^n ring-buffer pages have the layout described below.
|
|
|
|
|
|
|
|
If
|
|
|
|
.I perf_event_attr.sample_id_all
|
|
|
|
is set, then all event types will
|
|
|
|
have the sample_type selected fields related to where/when (identity)
|
|
|
|
an event took place (TID, TIME, ID, CPU, STREAM_ID) described in
|
|
|
|
.B PERF_RECORD_SAMPLE
|
|
|
|
below, it will be stashed just after the
|
2013-02-03 11:55:04 +00:00
|
|
|
.I perf_event_header
|
|
|
|
and the fields already present for the existing
|
2013-02-03 11:47:30 +00:00
|
|
|
fields, i.e., at the end of the payload.
|
|
|
|
That way a newer perf.data
|
|
|
|
file will be supported by older perf tools, with these new optional
|
|
|
|
fields being ignored.
|
|
|
|
|
|
|
|
The mmap values start with a header:
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct perf_event_header {
|
|
|
|
__u32 type;
|
|
|
|
__u16 misc;
|
|
|
|
__u16 size;
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
.in
|
|
|
|
|
|
|
|
Below, we describe the
|
|
|
|
.I perf_event_header
|
|
|
|
fields in more detail.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I type
|
|
|
|
The
|
|
|
|
.I type
|
|
|
|
value is one of the below.
|
|
|
|
The values in the corresponding record (that follows the header)
|
|
|
|
depend on the
|
|
|
|
.I type
|
|
|
|
selected as shown.
|
|
|
|
|
|
|
|
.RS
|
2013-02-03 11:55:04 +00:00
|
|
|
.TP 4
|
2013-02-03 11:47:30 +00:00
|
|
|
.B PERF_RECORD_MMAP
|
|
|
|
The MMAP events record the
|
|
|
|
.B PROT_EXEC
|
|
|
|
mappings so that we can correlate
|
2013-02-03 11:55:04 +00:00
|
|
|
user space IPs to code.
|
2013-02-03 11:47:30 +00:00
|
|
|
They have the following structure:
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct {
|
|
|
|
struct perf_event_header header;
|
|
|
|
u32 pid, tid;
|
|
|
|
u64 addr;
|
|
|
|
u64 len;
|
|
|
|
u64 pgoff;
|
|
|
|
char filename[];
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
.in
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_LOST
|
|
|
|
This record indicates when events are lost.
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct {
|
|
|
|
struct perf_event_header header;
|
|
|
|
u64 id;
|
|
|
|
u64 lost;
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
.in
|
|
|
|
|
|
|
|
.RS
|
|
|
|
.TP
|
|
|
|
.I id
|
|
|
|
is the unique event ID for the samples that were lost.
|
|
|
|
.TP
|
|
|
|
.I lost
|
|
|
|
is the number of events that were lost.
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_COMM
|
|
|
|
This record indicates a change in the process name.
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct {
|
|
|
|
struct perf_event_header header;
|
|
|
|
u32 pid, tid;
|
|
|
|
char comm[];
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
.in
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_EXIT
|
|
|
|
This record indicates a process exit event.
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct {
|
|
|
|
struct perf_event_header header;
|
|
|
|
u32 pid, ppid;
|
|
|
|
u32 tid, ptid;
|
|
|
|
u64 time;
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
.in
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.BR PERF_RECORD_THROTTLE ", " PERF_RECORD_UNTHROTTLE
|
|
|
|
This record indicates a throttle/unthrottle event.
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct {
|
|
|
|
struct perf_event_header header;
|
|
|
|
u64 time;
|
|
|
|
u64 id;
|
|
|
|
u64 stream_id;
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
.in
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_FORK
|
|
|
|
This record indicates a fork event.
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct {
|
|
|
|
struct perf_event_header header;
|
|
|
|
u32 pid, ppid;
|
|
|
|
u32 tid, ptid;
|
|
|
|
u64 time;
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
.in
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_READ
|
|
|
|
This record indicates a read event.
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct {
|
|
|
|
struct perf_event_header header;
|
|
|
|
u32 pid, tid;
|
|
|
|
struct read_format values;
|
|
|
|
};
|
|
|
|
.fi
|
|
|
|
.in
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_SAMPLE
|
|
|
|
This record indicates a sample.
|
|
|
|
|
|
|
|
.in +4n
|
|
|
|
.nf
|
|
|
|
struct {
|
|
|
|
struct perf_event_header header;
|
2013-02-03 11:55:04 +00:00
|
|
|
u64 ip; /* if PERF_SAMPLE_IP */
|
|
|
|
u32 pid, tid; /* if PERF_SAMPLE_TID */
|
|
|
|
u64 time; /* if PERF_SAMPLE_TIME */
|
|
|
|
u64 addr; /* if PERF_SAMPLE_ADDR */
|
|
|
|
u64 id; /* if PERF_SAMPLE_ID */
|
|
|
|
u64 stream_id; /* if PERF_SAMPLE_STREAM_ID */
|
|
|
|
u32 cpu, res; /* if PERF_SAMPLE_CPU */
|
|
|
|
u64 period; /* if PERF_SAMPLE_PERIOD */
|
2013-02-03 11:47:30 +00:00
|
|
|
struct read_format v; /* if PERF_SAMPLE_READ */
|
2013-02-03 11:55:04 +00:00
|
|
|
u64 nr; /* if PERF_SAMPLE_CALLCHAIN */
|
|
|
|
u64 ips[nr]; /* if PERF_SAMPLE_CALLCHAIN */
|
|
|
|
u32 size; /* if PERF_SAMPLE_RAW */
|
|
|
|
char data[size]; /* if PERF_SAMPLE_RAW */
|
|
|
|
u64 bnr; /* if PERF_SAMPLE_BRANCH_STACK */
|
|
|
|
struct perf_branch_entry lbr[bnr];
|
|
|
|
/* if PERF_SAMPLE_BRANCH_STACK */
|
|
|
|
u64 abi; /* if PERF_SAMPLE_REGS_USER */
|
|
|
|
u64 regs[weight(mask)];
|
|
|
|
/* if PERF_SAMPLE_REGS_USER */
|
|
|
|
u64 size; /* if PERF_SAMPLE_STACK_USER */
|
|
|
|
char data[size]; /* if PERF_SAMPLE_STACK_USER */
|
|
|
|
u64 dyn_size; /* if PERF_SAMPLE_STACK_USER */
|
2013-02-03 11:47:30 +00:00
|
|
|
};
|
|
|
|
.fi
|
|
|
|
|
|
|
|
.RS
|
|
|
|
.TP
|
|
|
|
.I ip
|
2013-02-03 11:55:04 +00:00
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_IP
|
|
|
|
is enabled, then a 64-bit instruction
|
2013-02-03 11:47:30 +00:00
|
|
|
pointer value is included.
|
|
|
|
|
|
|
|
.TP
|
2013-02-03 11:55:04 +00:00
|
|
|
.IR pid ", " tid
|
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_TID
|
|
|
|
is enabled, then a 32-bit process ID
|
|
|
|
and 32-bit thread ID are included.
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
.TP
|
|
|
|
.I time
|
2013-02-03 11:55:04 +00:00
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_TIME
|
|
|
|
is enabled, then a 64-bit timestamp
|
2013-02-03 11:47:30 +00:00
|
|
|
is included.
|
|
|
|
This is obtained via local_clock() which is a hardware timestamp
|
|
|
|
if available and the jiffies value if not.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I addr
|
2013-02-03 11:55:04 +00:00
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_ADDR
|
|
|
|
is enabled, then a 64-bit address is included.
|
2013-02-03 11:47:30 +00:00
|
|
|
This is usually the address of a tracepoint,
|
|
|
|
breakpoint, or software event; otherwise the value is 0.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I id
|
2013-02-03 11:55:04 +00:00
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_ID
|
|
|
|
is enabled, a 64-bit unique ID is included.
|
2013-02-03 11:47:30 +00:00
|
|
|
If the event is a member of an event group, the group leader ID is returned.
|
2013-02-03 11:55:04 +00:00
|
|
|
This ID is the same as the one returned by
|
|
|
|
.BR PERF_FORMAT_ID .
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
.TP
|
|
|
|
.I stream_id
|
2013-02-03 11:55:04 +00:00
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_STREAM_ID
|
|
|
|
is enabled, a 64-bit unique ID is included.
|
2013-02-03 11:47:30 +00:00
|
|
|
Unlike
|
|
|
|
.B PERF_SAMPLE_ID
|
|
|
|
the actual ID is returned, not the group leader.
|
2013-02-03 11:55:04 +00:00
|
|
|
This ID is the same as the one returned by
|
|
|
|
.BR PERF_FORMAT_ID .
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
.TP
|
2013-02-03 11:55:04 +00:00
|
|
|
.IR cpu ", " res
|
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_CPU
|
|
|
|
is enabled, this is a 32-bit value indicating
|
2013-02-03 11:47:30 +00:00
|
|
|
which CPU was being used, in addition to a reserved (unused)
|
|
|
|
32-bit value.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I period
|
2013-02-03 11:55:04 +00:00
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_PERIOD
|
|
|
|
is enabled, a 64-bit value indicating
|
2013-02-03 11:47:30 +00:00
|
|
|
the current sampling period is written.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I v
|
2013-02-03 11:55:04 +00:00
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_READ
|
|
|
|
is enabled, a structure of type read_format
|
2013-02-03 11:47:30 +00:00
|
|
|
is included which has values for all events in the event group.
|
|
|
|
The values included depend on the
|
|
|
|
.I read_format
|
2013-02-03 11:55:04 +00:00
|
|
|
value used at
|
|
|
|
.BR perf_event_open ()
|
|
|
|
time.
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
.TP
|
2013-02-03 11:55:04 +00:00
|
|
|
.IR nr ", " ips[nr]
|
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_CALLCHAIN
|
|
|
|
is enabled, then a 64-bit number is included
|
2013-02-03 11:47:30 +00:00
|
|
|
which indicates how many following 64-bit instruction pointers will
|
2013-02-03 11:55:04 +00:00
|
|
|
follow.
|
|
|
|
This is the current callchain.
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
.TP
|
2013-02-03 11:55:04 +00:00
|
|
|
.IR size ", " data
|
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_RAW
|
|
|
|
is enabled, then a 32-bit value indicating size
|
2013-02-03 11:47:30 +00:00
|
|
|
is included followed by an array of 8-bit values of length size.
|
|
|
|
The values are padded with 0 to have 64-bit alignment.
|
|
|
|
|
|
|
|
This RAW record data is opaque with respect to the ABI.
|
|
|
|
The ABI doesn't make any promises with respect to the stability
|
|
|
|
of its content, it may vary depending
|
|
|
|
on event, hardware, and kernel version.
|
|
|
|
|
|
|
|
.TP
|
2013-02-03 11:55:04 +00:00
|
|
|
.IR bnr ", " lbr[bnr]
|
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_BRANCH_STACK
|
|
|
|
is enabled, then a 64-bit value indicating
|
|
|
|
the number of records is included, followed by
|
|
|
|
.I bnr
|
|
|
|
.I perf_branch_entry
|
|
|
|
structures.
|
|
|
|
These structures have from, to, and flags values indicating
|
2013-02-03 11:47:30 +00:00
|
|
|
the from and to addresses from the branches on the callstack.
|
|
|
|
|
|
|
|
.TP
|
2013-02-03 11:55:04 +00:00
|
|
|
.IR abi ", " regs[weight(mask)]
|
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_REGS_USER
|
|
|
|
is enabled, then
|
2013-02-03 11:47:30 +00:00
|
|
|
[to be documented].
|
|
|
|
|
|
|
|
The
|
|
|
|
.I abi
|
|
|
|
field is one of
|
|
|
|
.BR PERF_SAMPLE_REGS_ABI_NONE ", " PERF_SAMPLE_REGS_ABI_32 " or "
|
2013-02-03 11:55:04 +00:00
|
|
|
.BR PERF_SAMPLE_REGS_ABI_64 .
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
.TP
|
2013-02-03 11:55:04 +00:00
|
|
|
.IR size ", " data[size] ", " dyn_size
|
|
|
|
If
|
|
|
|
.B PERF_SAMPLE_STACK_USER
|
|
|
|
is enabled, then
|
2013-02-03 11:47:30 +00:00
|
|
|
[to be documented].
|
|
|
|
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.RE
|
|
|
|
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I misc
|
|
|
|
The
|
|
|
|
.I misc
|
|
|
|
field contains additional information about the sample.
|
|
|
|
|
|
|
|
The CPU mode can be determined from this value by masking with
|
|
|
|
.B PERF_RECORD_MISC_CPUMODE_MASK
|
|
|
|
and looking for one of the following (note these are not
|
|
|
|
bitmasks, only one can be set at a time):
|
|
|
|
.RS
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_MISC_CPUMODE_UNKNOWN
|
|
|
|
Unknown CPU mode.
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_MISC_KERNEL
|
|
|
|
Sample happened in the kernel.
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_MISC_USER
|
|
|
|
Sample happened in user code.
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_MISC_HYPERVISOR
|
|
|
|
Sample happened in the hypervisor.
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_MISC_GUEST_KERNEL
|
|
|
|
Sample happened in the guest kernel.
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_MISC_GUEST_USER
|
|
|
|
Sample happened in guest user code.
|
|
|
|
.RE
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
In addition, one of the following bits can be set:
|
2013-02-03 11:47:30 +00:00
|
|
|
.RS
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_MISC_EXACT_IP
|
|
|
|
This indicates that the content of
|
|
|
|
.B PERF_SAMPLE_IP
|
|
|
|
points
|
|
|
|
to the actual instruction that triggered the event.
|
|
|
|
See also
|
|
|
|
.IR perf_event_attr.precise_ip .
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_RECORD_MISC_EXT_RESERVED
|
|
|
|
This indicates there is extended data available (currently not used).
|
|
|
|
|
|
|
|
.RE
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I size
|
|
|
|
This indicates the size of the record.
|
|
|
|
|
|
|
|
.RE
|
|
|
|
|
intro.1, time.1, _syscall.2, accept.2, brk.2, capget.2, faccessat.2, futimesat.2, gethostname.2, intro.2, ioprio_set.2, kill.2, madvise.2, mlock.2, mount.2, msgget.2, perf_event_open.2, poll.2, readv.2, sched_rr_get_interval.2, sched_setscheduler.2, select.2, select_tut.2, shmget.2, stat.2, timer_create.2, ustat.2, vfork.2, wait.2, alloca.3, atexit.3, catopen.3, crypt.3, dbopen.3, fenv.3, fopen.3, getaddrinfo_a.3, gethostbyname.3, getutent.3, intro.3, login.3, mallopt.3, queue.3, regex.3, sigpause.3, sigsetops.3, stdio.3, strftime.3, strptime.3, sysconf.3, ttyslot.3, undocumented.3, cciss.4, console_codes.4, hpsa.4, initrd.4, intro.4, rtc.4, st.4, tty_ioctl.4, wavelan.4, acct.5, charmap.5, dir_colors.5, hosts.5, intro.5, termcap.5, utmp.5, intro.6, armscii-8.7, boot.7, bootparam.7, capabilities.7, cpuset.7, credentials.7, ddp.7, epoll.7, glob.7, intro.7, ip.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, man-pages.7, man.7, math_error.7, netlink.7, numa.7, packet.7, path_resolution.7, pipe.7, pthreads.7, raw.7, rtnetlink.7, signal.7, socket.7, spufs.7, svipc.7, tcp.7, time.7, udp.7, udplite.7, unicode.7, unix.7, uri.7, utf-8.7, x25.7, intro.8: Global fix: use consistent capitalization in .SS headings
Capitalization in .SS sections across pages (and sometimes even
within a single page) is wildly inconsistent. Make it consistent.
Capitalize first word in heading, but otherwise use lower case,
except where English usage (e.g., proper nouns) or programming
language requirements (e.g., identifier names) dictate otherwise.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 14:08:38 +00:00
|
|
|
.SS "Signal overflow"
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
Events can be set to deliver a signal when a threshold is crossed.
|
|
|
|
The signal handler is set up using the
|
|
|
|
.BR poll (2),
|
|
|
|
.BR select (2),
|
|
|
|
.BR epoll (2)
|
|
|
|
and
|
|
|
|
.BR fcntl (2),
|
|
|
|
system calls.
|
|
|
|
|
|
|
|
To generate signals, sampling must be enabled
|
|
|
|
.RI ( sample_period
|
|
|
|
must have a non-zero value).
|
|
|
|
|
|
|
|
There are two ways to generate signals.
|
|
|
|
|
|
|
|
The first is to set a
|
|
|
|
.I wakeup_events
|
|
|
|
or
|
|
|
|
.I wakeup_watermark
|
|
|
|
value that will generate a signal if a certain number of samples
|
|
|
|
or bytes have been written to the mmap ring buffer.
|
2013-02-03 11:55:04 +00:00
|
|
|
In this case a signal of type
|
|
|
|
.B POLL_IN
|
|
|
|
is sent.
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
The other way is by use of the
|
2013-02-03 11:55:04 +00:00
|
|
|
.B PERF_EVENT_IOC_REFRESH
|
2013-02-03 11:47:30 +00:00
|
|
|
ioctl.
|
|
|
|
This ioctl adds to a counter that decrements each time the event overflows.
|
2013-02-03 11:55:04 +00:00
|
|
|
When non-zero, a
|
|
|
|
.B POLL_IN
|
|
|
|
signal is sent on overflow, but
|
|
|
|
once the value reaches 0, a signal is sent of type
|
|
|
|
.B POLL_HUP
|
|
|
|
and
|
2013-02-03 11:47:30 +00:00
|
|
|
the underlying event is disabled.
|
|
|
|
|
|
|
|
Note: on newer kernels (definitely noticed with 3.2)
|
2013-02-03 11:55:04 +00:00
|
|
|
.\" FIXME(Vince) : Find out when this was introduced
|
2013-02-03 11:47:30 +00:00
|
|
|
a signal is provided for every overflow, even if
|
|
|
|
.I wakeup_events
|
|
|
|
is not set.
|
|
|
|
|
|
|
|
.SS "rdpmc instruction"
|
|
|
|
Starting with Linux 3.4 on x86, you can use the
|
|
|
|
.I rdpmc
|
|
|
|
instruction to get low-latency reads without having to enter the kernel.
|
|
|
|
Note that using
|
|
|
|
.I rdpmc
|
|
|
|
is not necessarily faster than other methods for reading event values.
|
|
|
|
|
|
|
|
Support for this can be detected with the
|
|
|
|
.I cap_usr_rdpmc
|
|
|
|
field in the mmap page; documentation on how
|
|
|
|
to calculate event values can be found in that section.
|
|
|
|
|
|
|
|
.SS "perf_event ioctl calls"
|
|
|
|
.PP
|
|
|
|
Various ioctls act on
|
2013-02-03 11:55:04 +00:00
|
|
|
.BR perf_event_open ()
|
2013-02-03 11:47:30 +00:00
|
|
|
file descriptors
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_EVENT_IOC_ENABLE
|
2013-02-12 03:52:43 +00:00
|
|
|
Enables the individual event or event group specified by the
|
2013-02-03 11:55:04 +00:00
|
|
|
file descriptor argument.
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
The ioctl argument is ignored.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_EVENT_IOC_DISABLE
|
2013-02-12 03:52:43 +00:00
|
|
|
Disables the individual counter or event group specified by the
|
2013-02-03 11:55:04 +00:00
|
|
|
file descriptor argument.
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
Enabling or disabling the leader of a group enables or disables the
|
|
|
|
entire group; that is, while the group leader is disabled, none of the
|
|
|
|
counters in the group will count.
|
|
|
|
Enabling or disabling a member of a group other than the leader only
|
|
|
|
affects that counter; disabling a non-leader
|
|
|
|
stops that counter from counting but doesn't affect any other counter.
|
|
|
|
|
|
|
|
The ioctl argument is ignored.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_EVENT_IOC_REFRESH
|
|
|
|
Non-inherited overflow counters can use this
|
|
|
|
to enable a counter for a number of overflows specified by the argument,
|
|
|
|
after which it is disabled.
|
|
|
|
Subsequent calls of this ioctl add the argument value to the current
|
|
|
|
count.
|
2013-02-03 11:55:04 +00:00
|
|
|
A signal with
|
|
|
|
.B POLL_IN
|
|
|
|
set will happen on each overflow until the
|
|
|
|
count reaches 0; when that happens a signal with
|
|
|
|
POLL_HUP
|
|
|
|
set is sent and the event is disabled.
|
2013-02-03 11:47:30 +00:00
|
|
|
Using an argument of 0 is considered undefined behavior.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_EVENT_IOC_RESET
|
2013-02-12 03:52:43 +00:00
|
|
|
Reset the event count specified by the
|
2013-02-03 11:55:04 +00:00
|
|
|
file descriptor argumentto zero.
|
2013-02-03 11:47:30 +00:00
|
|
|
This only resets the counts; there is no way to reset the
|
|
|
|
multiplexing
|
|
|
|
.I time_enabled
|
|
|
|
or
|
|
|
|
.I time_running
|
|
|
|
values.
|
|
|
|
When sent to a group leader, only
|
|
|
|
the leader is reset (child events are not).
|
|
|
|
|
|
|
|
The ioctl argument is ignored.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_EVENT_IOC_PERIOD
|
|
|
|
IOC_PERIOD is the command to update the period; it
|
|
|
|
does not update the current period but instead defers until next.
|
|
|
|
|
|
|
|
The argument is a pointer to a 64-bit value containing the
|
|
|
|
desired new period.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.B PERF_EVENT_IOC_SET_OUTPUT
|
|
|
|
This tells the kernel to report event notifications to the specified
|
|
|
|
file descriptor rather than the default one.
|
|
|
|
The file descriptors must all be on the same CPU.
|
|
|
|
|
|
|
|
The argument specifies the desired file descriptor, or \-1 if
|
|
|
|
output should be ignored.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.BR PERF_EVENT_IOC_SET_FILTER " (Since Linux 2.6.33)"
|
|
|
|
This adds an ftrace filter to this event.
|
|
|
|
|
|
|
|
The argument is a pointer to the desired ftrace filter.
|
|
|
|
|
|
|
|
.SS "Using prctl"
|
|
|
|
A process can enable or disable all the event groups that are
|
|
|
|
attached to it using the
|
|
|
|
.BR prctl (2)
|
|
|
|
.B PR_TASK_PERF_EVENTS_ENABLE
|
|
|
|
and
|
|
|
|
.B PR_TASK_PERF_EVENTS_DISABLE
|
|
|
|
operations.
|
|
|
|
This applies to all counters on the current process, whether created by
|
|
|
|
this process or by another, and does not affect any counters that this
|
|
|
|
process has created on other processes.
|
|
|
|
It only enables or disables
|
|
|
|
the group leaders, not any other members in the groups.
|
|
|
|
|
|
|
|
.SS perf_event related configuration files
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
Files in
|
|
|
|
.I /proc/sys/kernel/
|
2013-02-03 11:47:30 +00:00
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
.RS 4
|
2013-02-03 11:47:30 +00:00
|
|
|
.TP
|
2013-02-03 11:55:04 +00:00
|
|
|
.I /proc/sys/kernel/perf_event_paranoid
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
The
|
|
|
|
.I perf_event_paranoid
|
|
|
|
file can be set to restrict access to the performance counters.
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
2 - only allow user-space measurements
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
1 - (default) allow both kernel and user measurements
|
|
|
|
|
|
|
|
0 - allow access to CPU-specific data but not raw tracepoint samples
|
|
|
|
|
|
|
|
\-1 - no restrictions
|
|
|
|
|
|
|
|
The existence of the
|
|
|
|
.I perf_event_paranoid
|
|
|
|
file is the official method for determining if a kernel supports
|
2013-02-03 11:55:04 +00:00
|
|
|
.BR perf_event_open ().
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
.TP
|
|
|
|
.I /proc/sys/kernel/perf_event_max_sample_rate
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
This sets the maximum sample rate.
|
|
|
|
Setting this too high can allow
|
2013-02-03 11:47:30 +00:00
|
|
|
users to sample at a rate that impacts overall machine performance
|
2013-02-03 11:55:04 +00:00
|
|
|
and potentially lock up the machine.
|
|
|
|
The default value is
|
2013-02-03 11:47:30 +00:00
|
|
|
100000 (samples per second).
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I /proc/sys/kernel/perf_event_mlock_kb
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
Maximum number of pages an unprivileged user can mlock (2) .
|
2013-02-03 11:47:30 +00:00
|
|
|
The default is 516 (kB).
|
|
|
|
.RE
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
Files in
|
|
|
|
.I /sys/bus/event_source/devices/
|
2013-02-03 11:47:30 +00:00
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
.RS 4
|
2013-02-03 11:47:30 +00:00
|
|
|
Since Linux 2.6.34 the kernel supports having multiple PMUs
|
|
|
|
available for monitoring.
|
|
|
|
Information on how to program these PMUs can be found under
|
|
|
|
.IR /sys/bus/event_source/devices/ .
|
|
|
|
Each subdirectory corresponds to a different PMU.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I /sys/bus/event_source/devices/*/type
|
|
|
|
This contains an integer that can be used in the
|
|
|
|
.I type
|
|
|
|
field of perf_event_attr to indicate you wish to use this PMU.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I /sys/bus/event_source/devices/*/rdpmc
|
|
|
|
[To be documented]
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I /sys/bus/event_source/devices/*/format/
|
|
|
|
This sub-directory contains information on what bits in the
|
|
|
|
.I config
|
|
|
|
field of perf_event_attr correspond to.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I /sys/bus/event_source/devices/*/events/
|
|
|
|
This sub-directory contains files with pre-defined events.
|
|
|
|
The contents are strings describing the event settings
|
|
|
|
expressed in terms of the fields found in the
|
|
|
|
.I ./format/
|
|
|
|
directory.
|
|
|
|
These are not necessarily complete lists of all events supported by
|
|
|
|
a PMU, but usually a subset of events deemed useful or interesting.
|
|
|
|
|
|
|
|
.TP
|
|
|
|
.I /sys/bus/event_source/devices/*/uevent
|
|
|
|
[To be documented]
|
|
|
|
|
|
|
|
.RE
|
|
|
|
|
|
|
|
|
|
|
|
.SH "RETURN VALUE"
|
|
|
|
.BR perf_event_open ()
|
|
|
|
returns the new file descriptor, or \-1 if an error occurred
|
|
|
|
(in which case,
|
|
|
|
.I errno
|
|
|
|
is set appropriately).
|
|
|
|
.SH ERRORS
|
|
|
|
.TP
|
|
|
|
.B EINVAL
|
|
|
|
Returned if the specified event is not available.
|
|
|
|
.TP
|
|
|
|
.B ENOSPC
|
|
|
|
Prior to Linux 3.3, if there was not enough room for the event,
|
|
|
|
.B ENOSPC
|
|
|
|
was returned.
|
|
|
|
Linus did not like this, and this was changed to
|
|
|
|
.BR EINVAL .
|
|
|
|
.B ENOSPC
|
|
|
|
is still returned if you try to read results into
|
|
|
|
too small of a buffer.
|
|
|
|
|
|
|
|
.SH VERSION
|
|
|
|
|
|
|
|
.BR perf_event_open ()
|
|
|
|
was introduced in Linux 2.6.31 but was called
|
|
|
|
.BR perf_counter_open () .
|
|
|
|
It was renamed in Linux 2.6.32.
|
|
|
|
|
|
|
|
.SH CONFORMING TO
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
This
|
|
|
|
.BR perf_event_open ()
|
|
|
|
system call Linux- specific
|
2013-02-03 11:47:30 +00:00
|
|
|
and should not be used in programs intended to be portable.
|
|
|
|
|
|
|
|
.SH NOTES
|
|
|
|
Glibc does not provide a wrapper for this system call; call it using
|
|
|
|
.BR syscall (2).
|
2013-02-03 11:55:04 +00:00
|
|
|
See the example below.
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
The official way of knowing if
|
2013-02-03 11:55:04 +00:00
|
|
|
.BR perf_event_open ()
|
2013-02-03 11:47:30 +00:00
|
|
|
support is enabled is checking
|
|
|
|
for the existence of the file
|
2013-02-03 11:55:04 +00:00
|
|
|
.IR /proc/sys/kernel/perf_event_paranoid .
|
2013-02-03 11:47:30 +00:00
|
|
|
|
|
|
|
.SH BUGS
|
|
|
|
|
|
|
|
The
|
|
|
|
.B F_SETOWN_EX
|
|
|
|
option to
|
2013-02-03 11:55:04 +00:00
|
|
|
.BR fcntl (2)
|
2013-02-03 11:47:30 +00:00
|
|
|
is needed to properly get overflow signals in threads.
|
|
|
|
This was introduced in Linux 2.6.32.
|
|
|
|
|
|
|
|
Prior to Linux 2.6.33 (at least for x86) the kernel did not check
|
|
|
|
if events could be scheduled together until read time.
|
|
|
|
The same happens on all known kernels if the NMI watchdog is enabled.
|
|
|
|
This means to see if a given set of events works you have to
|
|
|
|
.BR perf_event_open (),
|
|
|
|
start, then read before you know for sure you
|
|
|
|
can get valid measurements.
|
|
|
|
|
|
|
|
Prior to Linux 2.6.34 event constraints were not enforced by the kernel.
|
|
|
|
In that case, some events would silently return "0" if the kernel
|
|
|
|
scheduled them in an improper counter slot.
|
|
|
|
|
|
|
|
Prior to Linux 2.6.34 there was a bug when multiplexing where the
|
|
|
|
wrong results could be returned.
|
|
|
|
|
|
|
|
Kernels from Linux 2.6.35 to Linux 2.6.39 can quickly crash the kernel if
|
|
|
|
"inherit" is enabled and many threads are started.
|
|
|
|
|
|
|
|
Prior to Linux 2.6.35,
|
|
|
|
.B PERF_FORMAT_GROUP
|
|
|
|
did not work with attached processes.
|
|
|
|
|
|
|
|
In older Linux 2.6 versions,
|
|
|
|
refreshing an event group leader refreshed all siblings,
|
|
|
|
and refreshing with a parameter of 0 enabled infinite refresh.
|
|
|
|
This behavior is unsupported and should not be relied on.
|
|
|
|
|
|
|
|
There is a bug in the kernel code between
|
|
|
|
Linux 2.6.36 and Linux 3.0 that ignores the
|
|
|
|
"watermark" field and acts as if a wakeup_event
|
|
|
|
was chosen if the union has a
|
|
|
|
non-zero value in it.
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
Always double-check your results!
|
|
|
|
Various generalized events have had wrong values.
|
2013-02-03 11:47:30 +00:00
|
|
|
For example, retired branches measured
|
|
|
|
the wrong thing on AMD machines until Linux 2.6.35.
|
|
|
|
|
|
|
|
.SH EXAMPLE
|
|
|
|
The following is a short example that measures the total
|
2013-02-03 11:55:04 +00:00
|
|
|
instruction count of a call to
|
|
|
|
.BR printf (3).
|
2013-02-03 11:47:30 +00:00
|
|
|
.nf
|
|
|
|
|
|
|
|
#include <stdlib.h>
|
|
|
|
#include <stdio.h>
|
|
|
|
#include <unistd.h>
|
|
|
|
#include <string.h>
|
|
|
|
#include <sys/ioctl.h>
|
|
|
|
#include <linux/perf_event.h>
|
|
|
|
#include <asm/unistd.h>
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
long
|
|
|
|
perf_event_open(struct perf_event_attr *hw_event, pid_t pid,
|
|
|
|
int cpu, int group_fd, unsigned long flags)
|
2013-02-03 11:47:30 +00:00
|
|
|
{
|
|
|
|
int ret;
|
|
|
|
|
2013-02-03 11:55:04 +00:00
|
|
|
ret = syscall(__NR_perf_event_open, hw_event, pid, cpu,
|
|
|
|
group_fd, flags);
|
2013-02-03 11:47:30 +00:00
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
int
|
|
|
|
main(int argc, char **argv)
|
|
|
|
{
|
|
|
|
|
|
|
|
struct perf_event_attr pe;
|
|
|
|
long long count;
|
|
|
|
int fd;
|
|
|
|
|
|
|
|
memset(&pe, 0, sizeof(struct perf_event_attr));
|
|
|
|
pe.type = PERF_TYPE_HARDWARE;
|
|
|
|
pe.size = sizeof(struct perf_event_attr);
|
|
|
|
pe.config = PERF_COUNT_HW_INSTRUCTIONS;
|
|
|
|
pe.disabled = 1;
|
|
|
|
pe.exclude_kernel = 1;
|
|
|
|
pe.exclude_hv = 1;
|
|
|
|
|
|
|
|
fd = perf_event_open(&pe, 0, \-1, \-1, 0);
|
2013-02-03 11:55:04 +00:00
|
|
|
if (fd == \-1) {
|
2013-02-03 11:47:30 +00:00
|
|
|
fprintf(stderr, "Error opening leader %llx\\n", pe.config);
|
2013-02-03 11:55:04 +00:00
|
|
|
exit(EXIT_FAILURE);
|
2013-02-03 11:47:30 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
ioctl(fd, PERF_EVENT_IOC_RESET, 0);
|
|
|
|
ioctl(fd, PERF_EVENT_IOC_ENABLE, 0);
|
|
|
|
|
|
|
|
printf("Measuring instruction count for this printf\\n");
|
|
|
|
|
|
|
|
ioctl(fd, PERF_EVENT_IOC_DISABLE, 0);
|
|
|
|
read(fd, &count, sizeof(long long));
|
|
|
|
|
|
|
|
printf("Used %lld instructions\\n", count);
|
|
|
|
|
|
|
|
close(fd);
|
|
|
|
}
|
|
|
|
.fi
|
|
|
|
|
|
|
|
.SH "SEE ALSO"
|
|
|
|
.BR fcntl (2),
|
|
|
|
.BR mmap (2),
|
|
|
|
.BR open (2),
|
|
|
|
.BR prctl (2),
|
|
|
|
.BR read (2)
|