Commit-ID: b32fd2f3f667c8a94f2f6bc2fb88a607be8f3229
Gitweb: http://git.kernel.org/tip/b32fd2f3f667c8a94f2f6bc2fb88a607be8f3229
Author: Jiri Olsa <jo...@kernel.org>
AuthorDate: Fri, 14 Jul 2017 18:35:51 +0200
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Tue, 18 Jul 2017 11:06:12 +0200
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 <jo...@kernel.org>
Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
Cc: Kan Liang <kan.li...@intel.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijls...@chello.nl>
Cc: Thomas Gleixner <t...@linutronix.de>
Link: http://lkml.kernel.org/r/20170714163551.19459-1-jo...@kernel.org
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
arch/x86/events/intel/ds.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 2ca4d2d..6dc8a59 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;
}
}
