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author | Jiri Olsa <jolsa@kernel.org> | 2017-07-14 18:35:51 +0200 |
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committer | Ingo Molnar <mingo@kernel.org> | 2017-07-18 14:13:41 +0200 |
commit | dc853e26f73e903e0c87e24f2695b5dcf33b3bc1 (patch) | |
tree | 0b6539cacfa3cd42d24d35851674988226359c94 /arch/x86 | |
parent | dd0b06b551f6b14da19582e301814746d838965a (diff) | |
download | linux-dc853e26f73e903e0c87e24f2695b5dcf33b3bc1.tar.gz linux-dc853e26f73e903e0c87e24f2695b5dcf33b3bc1.tar.bz2 linux-dc853e26f73e903e0c87e24f2695b5dcf33b3bc1.zip |
perf/x86/intel: Fix debug_store reset field for freq events
There's a bug in PEBs event enabling code, that prevents PEBS
freq events to work properly after non freq PEBS event was run.
freq events - perf_event_attr::freq set
-F <freq> option of perf record
PEBS events - perf_event_attr::precise_ip > 0
default for perf record
Like in following example with CPU 0 busy, we expect ~10000 samples
for following perf tool run:
# perf record -F 10000 -C 0 sleep 1
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.640 MB perf.data (10031 samples) ]
Everything's fine, but once we run non freq PEBS event like:
# perf record -c 10000 -C 0 sleep 1
[ perf record: Woken up 4 times to write data ]
[ perf record: Captured and wrote 1.053 MB perf.data (20061 samples) ]
the freq events start to fail like this:
# perf record -F 10000 -C 0 sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.185 MB perf.data (40 samples) ]
The issue is in non freq PEBs event initialization of debug_store reset
field, which value is used to auto-reload the counter value after PEBS
event drain. This value is not being used for PEBS freq events, but once
we run non freq event it stays in debug_store data and screws the
sample_freq counting for PEBS freq events.
Setting the reset field to 0 for freq events.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170714163551.19459-1-jolsa@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
-rw-r--r-- | arch/x86/events/intel/ds.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c index 2ca4d2d7b5fc..6dc8a59e1bfb 100644 --- a/arch/x86/events/intel/ds.c +++ b/arch/x86/events/intel/ds.c @@ -895,6 +895,8 @@ void intel_pmu_pebs_enable(struct perf_event *event) if (hwc->flags & PERF_X86_EVENT_AUTO_RELOAD) { ds->pebs_event_reset[hwc->idx] = (u64)(-hwc->sample_period) & x86_pmu.cntval_mask; + } else { + ds->pebs_event_reset[hwc->idx] = 0; } } |