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authorPeter Zijlstra <peterz@infradead.org>2015-02-20 14:05:38 +0100
committerIngo Molnar <mingo@kernel.org>2015-03-27 10:13:22 +0100
commit34f439278cef7b1177f8ce24f9fc81dfc6221d3b (patch)
tree8bd86bf3d73aff36e8bee13c0102c7ae7e44e40c /include/uapi/linux/perf_event.h
parentb381e63b48a0b6befc7b4e55408c39012a0dcf8c (diff)
perf: Add per event clockid support
While thinking on the whole clock discussion it occurred to me we have two distinct uses of time: 1) the tracking of event/ctx/cgroup enabled/running/stopped times which includes the self-monitoring support in struct perf_event_mmap_page. 2) the actual timestamps visible in the data records. And we've been conflating them. The first is all about tracking time deltas, nobody should really care in what time base that happens, its all relative information, as long as its internally consistent it works. The second however is what people are worried about when having to merge their data with external sources. And here we have the discussion on MONOTONIC vs MONOTONIC_RAW etc.. Where MONOTONIC is good for correlating between machines (static offset), MONOTNIC_RAW is required for correlating against a fixed rate hardware clock. This means configurability; now 1) makes that hard because it needs to be internally consistent across groups of unrelated events; which is why we had to have a global perf_clock(). However, for 2) it doesn't really matter, perf itself doesn't care what it writes into the buffer. The below patch makes the distinction between these two cases by adding perf_event_clock() which is used for the second case. It further makes this configurable on a per-event basis, but adds a few sanity checks such that we cannot combine events with different clocks in confusing ways. And since we then have per-event configurability we might as well retain the 'legacy' behaviour as a default. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/uapi/linux/perf_event.h')
-rw-r--r--include/uapi/linux/perf_event.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 1e3cd07cf76e..3bb40ddadbe5 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -326,7 +326,8 @@ struct perf_event_attr {
exclude_callchain_user : 1, /* exclude user callchains */
mmap2 : 1, /* include mmap with inode data */
comm_exec : 1, /* flag comm events that are due to an exec */
- __reserved_1 : 39;
+ use_clockid : 1, /* use @clockid for time fields */
+ __reserved_1 : 38;
union {
__u32 wakeup_events; /* wakeup every n events */
@@ -355,8 +356,7 @@ struct perf_event_attr {
*/
__u32 sample_stack_user;
- /* Align to u64. */
- __u32 __reserved_2;
+ __s32 clockid;
/*
* Defines set of regs to dump for each sample
* state captured on: