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| author | Vince Weaver <vincent.weaver@maine.edu> | 2016-10-18 13:22:20 -0400 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2016-10-19 08:53:47 +0200 |
| commit | 9277a75d393169affe4165e4871b562c15c8e026 (patch) | |
| tree | b61fdff645fbb92763802e7498450d8b4f812e47 | |
| parent | 9227137a38bcbe20736e4b3405468f49df7d66be (diff) | |
| download | man-pages-9277a75d393169affe4165e4871b562c15c8e026.tar.gz | |
perf_event_open.2: PERF_RECORD_SWITCH support
Linux 4.3 introduced two new record types for recording context
switches: PERF_RECORD_SWITCH and PERF_RECORD_SWITCH_CPU_WIDE.
The advantage over the existing tracepoint and software context
switch events is primarily that full switch in/out data can be
gathered even in the face of restrictive perf_event_paranoid
settings.
Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>
| -rw-r--r-- | man2/perf_event_open.2 | 89 |
1 files changed, 84 insertions, 5 deletions
diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 68b99bb7f6..04a0cf5ca2 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -243,8 +243,9 @@ struct perf_event_attr { comm_exec : 1, /* flag comm events that are due to exec */ use_clockid : 1, /* use clockid for time fields */ + context_switch : 1, /* context switch data */ - __reserved_1 : 38; + __reserved_1 : 37; union { __u32 wakeup_events; /* wakeup every n events */ @@ -1112,6 +1113,21 @@ field. This can make it easier to correlate perf sample times with timestamps generated by other tools. .TP +.IR "context_switch" " (since Linux 4.3)" +.\" commit 45ac1403f564f411c6a383a2448688ba8dd705a4 +This enables the generation of +.B PERF_RECORD_SWITCH +records when a context switch occurs. +It also enables the generation of +.B PERF_RECORD_SWITCH_CPU_WIDE +records when sampling in cpu-wide mode. +This functionality is in addition to existing tracepoint and +software events for measuring context switches. +The advantage of this method is that it will give full +information event with strict +.I perf_event_paranoid +settings. +.TP .IR "wakeup_events" ", " "wakeup_watermark" This union sets how many samples .RI ( wakeup_events ) @@ -1792,7 +1808,8 @@ Sample happened in guest user code. .RE .RS -In addition, one of the following bits can be set: +The following three statuses are generated by +different record types so they alias to the same bit: .TP .BR PERF_RECORD_MISC_MMAP_DATA " (since Linux 3.10)" .\" commit 2fe85427e3bf65d791700d065132772fc26e4d75 @@ -1807,9 +1824,18 @@ record on kernels more recent than Linux 3.16 if a process name change was caused by an .BR exec (2) system call. -It is an alias for -.B PERF_RECORD_MISC_MMAP_DATA -since the two values would not be set in the same record. +.TP +.BR PERF_RECORD_MISC_SWITCH_OUT " (since Linux 4.3)" +.\" commit 45ac1403f564f411c6a383a2448688ba8dd705a4 +When a +.BR PERF_RECORD_SWITCH " or " PERF_RECORD_SWITCH_CPU_WIDE +record is generated this bit indicates that the +context switch is away from the current process +(instead of in to the current process). +.RE + +.RS +In addition, the following bits can be set: .TP .B PERF_RECORD_MISC_EXACT_IP This indicates that the content of @@ -2583,6 +2609,59 @@ struct { .I lost the number of potentially lost samples. .RE +.TP +.BR PERF_RECORD_SWITCH " (since Linux 4.3)" +\" commit 45ac1403f564f411c6a383a2448688ba8dd705a4 +This record indicates a context switch has happened. +The +.B PERF_RECORD_MISC_SWITCH_OUT +bit in the +.I misc +field indicates whether it was a context switch into +or away from the current process. + +.in +4n +.nf +struct { + struct perf_event_header header; + struct sample_id sample_id; +}; +.fi +.TP +.BR PERF_RECORD_SWITCH_CPU_WIDE " (since Linux 4.3)" +\" commit 45ac1403f564f411c6a383a2448688ba8dd705a4 +As with +.B PERF_RECORD_SWITCH +this record indicates a context switch has happened, +but it only occurs when sampling in cpu-wide mode +and provides additional information on the process +being switched to/from. +The +.B PERF_RECORD_MISC_SWITCH_OUT +bit in the +.I misc +field indicates whether it was a context switch into +or away from the current process. + +.in +4n +.nf +struct { + struct perf_event_header header; + u32 next_prev_pid; + u32 next_prev_tid; + struct sample_id sample_id; +}; +.fi +.RS +.TP +.I next_prev_pid +The process id of the previous (if switching in) +or next (if switching out) process on the CPU. +.TP +.I next_prev_tid +The thread id of the previous (if switching in) +or next (if switching out) thread on the CPU. +.RE .RE .SS Overflow handling Events can be set to notify when a threshold is crossed, |