2015-02-03 14:43:21 +00:00
|
|
|
.\" Copyright (C) 2015 Michael Kerrisk <mtk.manpages@gmail.com>
|
|
|
|
.\"
|
|
|
|
.\" %%%LICENSE_START(GPLv2+)
|
|
|
|
.\"
|
|
|
|
.\" This program is free software; you can redistribute it and/or modify
|
|
|
|
.\" it under the terms of the GNU General Public License as published by
|
|
|
|
.\" the Free Software Foundation; either version 2 of the License, or
|
|
|
|
.\" (at your option) any later version.
|
|
|
|
.\"
|
|
|
|
.\" This program is distributed in the hope that it will be useful,
|
|
|
|
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
|
|
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
|
|
.\" GNU General Public License for more details.
|
|
|
|
.\"
|
|
|
|
.\" You should have received a copy of the GNU General Public
|
|
|
|
.\" License along with this manual; if not, see
|
|
|
|
.\" <http://www.gnu.org/licenses/>.
|
|
|
|
.\" %%%LICENSE_END
|
|
|
|
.\"
|
locale.1, localedef.1, _exit.2, accept.2, access.2, acct.2, adjtimex.2, bdflush.2, bind.2, bpf.2, brk.2, chdir.2, chmod.2, chown.2, chroot.2, clock_nanosleep.2, clone.2, close.2, connect.2, copy_file_range.2, create_module.2, delete_module.2, dup.2, epoll_ctl.2, eventfd.2, execve.2, fallocate.2, fanotify_init.2, fcntl.2, flock.2, fork.2, fsync.2, futex.2, get_kernel_syms.2, getdomainname.2, getgroups.2, gethostname.2, getpagesize.2, getpeername.2, getsid.2, getsockname.2, getsockopt.2, gettimeofday.2, init_module.2, ioctl.2, ioctl_list.2, ioperm.2, iopl.2, kexec_load.2, kill.2, killpg.2, link.2, listen.2, llseek.2, lseek.2, madvise.2, memfd_create.2, mincore.2, mkdir.2, mknod.2, mmap.2, mount.2, nanosleep.2, nice.2, open.2, personality.2, pipe.2, poll.2, posix_fadvise.2, read.2, readahead.2, readlink.2, readv.2, recv.2, recvmmsg.2, rename.2, request_key.2, sched_setaffinity.2, sched_setattr.2, select.2, select_tut.2, semctl.2, semop.2, send.2, sendfile.2, sendmmsg.2, seteuid.2, setns.2, setpgid.2, setreuid.2, shutdown.2, sigaction.2, sigaltstack.2, signal.2, signalfd.2, sigpending.2, sigprocmask.2, sigsuspend.2, socketpair.2, splice.2, stat.2, statfs.2, stime.2, symlink.2, sync.2, syscall.2, syscalls.2, times.2, truncate.2, unlink.2, unshare.2, uselib.2, utimensat.2, vfork.2, vhangup.2, wait.2, wait4.2, write.2, a64l.3, abs.3, acos.3, acosh.3, addseverity.3, adjtime.3, aio_read.3, aio_write.3, asin.3, asinh.3, atan.3, atan2.3, atanh.3, atoi.3, backtrace.3, cbrt.3, ceil.3, cfree.3, clearenv.3, clock_getcpuclockid.3, clog10.3, cmsg.3, copysign.3, cos.3, cosh.3, ctermid.3, ctime.3, daemon.3, dirfd.3, div.3, dl_iterate_phdr.3, drand48.3, drand48_r.3, dysize.3, ecvt.3, ecvt_r.3, endian.3, erf.3, erfc.3, errno.3, exec.3, exp.3, exp2.3, expm1.3, fabs.3, fdim.3, ferror.3, fexecve.3, ffs.3, fgetgrent.3, fgetpwent.3, finite.3, flockfile.3, floor.3, fma.3, fmax.3, fmin.3, fmod.3, fopen.3, fpclassify.3, frexp.3, fseeko.3, fts.3, futimes.3, fwide.3, gamma.3, gcvt.3, getaddrinfo.3, getcwd.3, getdate.3, getdirentries.3, getdtablesize.3, getgrent.3, getgrent_r.3, getgrnam.3, getgrouplist.3, gethostbyname.3, gethostid.3, getline.3, getloadavg.3, getmntent.3, getnameinfo.3, getnetent_r.3, getpass.3, getprotoent_r.3, getpwent.3, getpwent_r.3, getpwnam.3, getrpcent_r.3, getservent_r.3, getspnam.3, getsubopt.3, getusershell.3, getutent.3, getw.3, gsignal.3, hypot.3, ilogb.3, inet.3, initgroups.3, insque.3, isalpha.3, isgreater.3, iswblank.3, j0.3, ldexp.3, lgamma.3, lio_listio.3, lockf.3, log.3, log10.3, log1p.3, log2.3, logb.3, lrint.3, lround.3, makedev.3, matherr.3, mbsnrtowcs.3, mkdtemp.3, mkfifo.3, mkstemp.3, mktemp.3, modf.3, mq_close.3, mq_getattr.3, mq_notify.3, mq_receive.3, mq_send.3, nan.3, nextafter.3, on_exit.3, open_memstream.3, opendir.3, perror.3, popen.3, posix_fallocate.3, posix_madvise.3, posix_memalign.3, posix_openpt.3, posix_spawn.3, pow.3, printf.3, profil.3, psignal.3, pthread_attr_setstack.3, pthread_setaffinity_np.3, putenv.3, putpwent.3, qecvt.3, rand.3, random.3, random_r.3, rcmd.3, readdir.3, realpath.3, remainder.3, remquo.3, rexec.3, rint.3, round.3, rpc.3, rpmatch.3, scalb.3, scalbln.3, scandir.3, scanf.3, seekdir.3, sem_wait.3, setbuf.3, setenv.3, setjmp.3, setnetgrent.3, siginterrupt.3, signbit.3, significand.3, sigset.3, sigsetops.3, sigvec.3, sigwait.3, sin.3, sinh.3, sleep.3, sockatmark.3, sqrt.3, statvfs.3, stpcpy.3, stpncpy.3, strdup.3, strerror.3, strftime.3, strlen.3, strnlen.3, strsep.3, strsignal.3, strtod.3, strtok.3, strtol.3, strtoul.3, syslog.3, system.3, tan.3, tanh.3, telldir.3, tempnam.3, termios.3, tgamma.3, timegm.3, timeradd.3, tmpfile.3, tmpnam.3, toascii.3, trunc.3, ttyslot.3, tzset.3, ualarm.3, unlocked_stdio.3, usleep.3, wcpcpy.3, wcpncpy.3, wcscasecmp.3, wcsdup.3, wcsncasecmp.3, wcsnlen.3, wcsnrtombs.3, wprintf.3, y0.3, pts.4, st.4, tty_ioctl.4, elf.5, gai.conf.5, group.5, locale.5, nsswitch.conf.5, proc.5, utmp.5, aio.7, capabilities.7, credentials.7, environ.7, epoll.7, fanotify.7, feature_test_macros.7, inotify.7, ip.7, mq_overview.7, namespaces.7, pipe.7, signal.7, socket.7, standards.7, svipc.7, symlink.7, time.7, unicode.7, unix.7: tstamp
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2016-03-15 03:46:01 +00:00
|
|
|
.TH POSIX_MADVISE 3 2016-03-15 Linux "Linux Programmer's Manual"
|
2015-02-03 14:43:21 +00:00
|
|
|
.SH NAME
|
|
|
|
posix_madvise \- give advice about patterns of memory usage
|
|
|
|
.SH SYNOPSIS
|
|
|
|
.nf
|
|
|
|
.B #include <sys/mman.h>
|
|
|
|
|
|
|
|
.BI "int posix_madvise(void *" addr ", size_t " len ", int " advice );
|
|
|
|
.fi
|
|
|
|
|
|
|
|
.in -4n
|
|
|
|
Feature Test Macro Requirements for glibc (see
|
|
|
|
.BR feature_test_macros (7)):
|
|
|
|
.in
|
|
|
|
.sp
|
|
|
|
.BR posix_madvise ():
|
|
|
|
.br
|
|
|
|
.RS 4
|
|
|
|
.ad l
|
brk.2, chroot.2, clock_nanosleep.2, getpagesize.2, posix_fadvise.2, select.2, select_tut.2, seteuid.2, clock_getcpuclockid.3, ecvt.3, exp2.3, fseeko.3, gcvt.3, getdtablesize.3, getpass.3, getw.3, log2.3, mktemp.3, mq_receive.3, mq_send.3, posix_fallocate.3, posix_madvise.3, posix_memalign.3, pthread_attr_setstack.3, rint.3, sem_wait.3, setenv.3, sockatmark.3, strerror.3: Simplify FTM requirements
Looking at <features.h> (or feature_test_macros(7)), one can
see that when _XOPEN_SOURCE is defined with the value 600
(or greater), then _POSIX_C_SOURCE is defined with the value
200112L (or greater). Therefore, terms in the man pages such as
_XOPEN_SOURCE\ >=\ 600 || _POSIX_C_SOURCE\ >=\ 200112L
can be simpified to:
_POSIX_C_SOURCE\ >=\ 200112L
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2016-02-08 09:52:51 +00:00
|
|
|
_POSIX_C_SOURCE >= 200112L
|
2015-02-03 14:43:21 +00:00
|
|
|
.RE
|
|
|
|
.ad
|
|
|
|
.SH DESCRIPTION
|
|
|
|
The
|
|
|
|
.BR posix_madvise ()
|
|
|
|
function allows an application to advise the system about its expected
|
|
|
|
patterns of usage of memory in the address range starting at
|
|
|
|
.I addr
|
|
|
|
and continuing for
|
|
|
|
.I len
|
|
|
|
bytes.
|
|
|
|
The system is free to use this advice in order to improve the performance
|
|
|
|
of memory accesses (or to ignore the advice altogether), but calling
|
|
|
|
.BR posix_madvise ()
|
|
|
|
shall not affect the semantics of access to memory in the specified range.
|
|
|
|
|
|
|
|
The
|
|
|
|
.I advice
|
|
|
|
argument is one of the following:
|
|
|
|
.TP
|
|
|
|
.B POSIX_MADV_NORMAL
|
|
|
|
The application has no special advice regarding its memory usage patterns
|
|
|
|
for the specified address range.
|
|
|
|
This is the default behavior.
|
|
|
|
.TP
|
|
|
|
.B POSIX_MADV_SEQUENTIAL
|
|
|
|
The application expects to access the specified address range sequentially,
|
|
|
|
running from lower addresses to higher addresses.
|
|
|
|
Hence, pages in this region can be aggressively read ahead,
|
|
|
|
and may be freed soon after they are accessed.
|
|
|
|
.TP
|
|
|
|
.B POSIX_MADV_RANDOM
|
|
|
|
The application expects to access the specified address range randomly.
|
|
|
|
Thus, read ahead may be less useful than normally.
|
|
|
|
.TP
|
|
|
|
.B POSIX_MADV_WILLNEED
|
|
|
|
The application expects to access the specified address range
|
|
|
|
in the near future.
|
|
|
|
Thus, read ahead may be beneficial.
|
|
|
|
.TP
|
|
|
|
.B POSIX_MADV_DONTNEED
|
|
|
|
The application expects that it will not access the specified address range
|
|
|
|
in the near future.
|
|
|
|
.SH RETURN VALUE
|
|
|
|
On success,
|
|
|
|
.BR posix_madvise ()
|
|
|
|
returns 0.
|
|
|
|
On failure, it returns a positive error number.
|
|
|
|
.SH ERRORS
|
|
|
|
.TP
|
|
|
|
.B EINVAL
|
|
|
|
.I addr
|
|
|
|
is not a multiple of the system page size or
|
|
|
|
.I len
|
|
|
|
is negative.
|
|
|
|
.TP
|
|
|
|
.B EINVAL
|
|
|
|
.I advice
|
|
|
|
is invalid.
|
|
|
|
.TP
|
|
|
|
.B ENOMEM
|
|
|
|
Addresses in the specified range are partially or completely outside
|
|
|
|
the caller's address space.
|
|
|
|
.SH VERSIONS
|
|
|
|
Support for
|
|
|
|
.BR posix_madvise ()
|
|
|
|
first appeared in glibc version 2.2.
|
|
|
|
.SH CONFORMING TO
|
|
|
|
POSIX.1-2001.
|
|
|
|
|
|
|
|
POSIX.1-2008 specifies a further value for
|
|
|
|
.IR advice ,
|
|
|
|
.BR POSIX_FADV_NOREUSE ,
|
|
|
|
meaning that the specified data will be accessed only once.
|
|
|
|
This value is not currently supported.
|
|
|
|
.SH NOTES
|
|
|
|
POSIX.1 permits an implementation to generate an error if
|
|
|
|
.I len
|
|
|
|
is 0.
|
|
|
|
On Linux, specifying
|
|
|
|
.I len
|
|
|
|
as 0 is permitted (as a successful no-op).
|
|
|
|
|
|
|
|
In glibc, this function is implemented using
|
|
|
|
.BR madvise (2).
|
|
|
|
However, since glibc 2.6,
|
|
|
|
.BR POSIX_MADV_DONTNEED
|
|
|
|
is treated as a no-op, because the corresponding
|
|
|
|
.BR madvise (2)
|
|
|
|
value,
|
|
|
|
.BR MADV_DONTNEED ,
|
|
|
|
has destructive semantics.
|
|
|
|
.SH SEE ALSO
|
|
|
|
.BR madvise (2),
|
|
|
|
.BR posix_fadvise (2)
|