diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
index ec4463c85..257be7c06 100644
--- a/man2/perf_event_open.2
+++ b/man2/perf_event_open.2
@@ -233,7 +233,9 @@ struct perf_event_attr {
                                 /* exclude user callchains */
           mmap2          :  1,  /* include mmap with inode data */
           comm_exec      :  1,  /* flag comm events that are due to exec */
-          __reserved_1   : 39;
+          use_clockid    :  1,  /* use clockid for time fields */
+
+          __reserved_1   : 38;
 
     union {
         __u32 wakeup_events;    /* wakeup every n events */
@@ -255,7 +257,7 @@ struct perf_event_attr {
     __u64 sample_regs_user;     /* user regs to dump on samples */
     __u32 sample_stack_user;    /* size of stack to dump on
                                    samples */
-    __u32 __reserved_2;         /* Align to u64 */
+    __s32 clockid;              /* clock to use for time fields */
     __u64 sample_regs_intr;     /* regs to dump on samples */
 };
 .fi
@@ -1086,6 +1088,15 @@ reported was caused by a call to
 This allows tools to distinguish between the various
 types of process renaming.
 .TP
+.IR "use_clockid" " (since Linux 4.1)"
+.\" commit 34f439278cef7b1177f8ce24f9fc81dfc6221d3b
+This allows selecting which internal Linux clock to use
+when generating timestamps via the
+.I clockid
+field.
+This can make it easier to correlate perf sample times with
+timestamps generated by other tools.
+.TP
 .IR "wakeup_events" ", " "wakeup_watermark"
 This union sets how many samples
 .RI ( wakeup_events )
@@ -1260,6 +1271,19 @@ described in the kernel header
 This defines the size of the user stack to dump if
 .B PERF_SAMPLE_STACK_USER
 is specified.
+.TP
+.IR "clockid" " (since Linux 4.1)"
+.\" commit 34f439278cef7b1177f8ce24f9fc81dfc6221d3b
+If
+.I use_clockid
+is set, then this field selects which internal Linux timer to
+use for timestamps.
+The available timers are defined in
+.IR linux/time.h ,
+with
+.BR CLOCK_MONOTONIC , CLOCK_MONOTONIC_RAW , CLOCK_REALTIME ,
+.BR CLOCK_BOOTTIME ", and " CLOCK_TAI
+currently supported.
 .SS Reading results
 Once a
 .BR perf_event_open ()