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perf/x86: Add PERF_X86_EVENT_NEEDS_BRANCH_STACK flag

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Currently, branch_sample_type !=0 is used to check whether a branch
stack setup is required. But it doesn't check the sample type,
unnecessary branch stack setup may be done for a counting event. E.g.,
perf record -e "{branch-instructions,branch-misses}:S" -j any
Also, the event only with the new PERF_SAMPLE_BRANCH_COUNTERS branch
sample type may not require a branch stack setup either.

Add a new flag NEEDS_BRANCH_STACK to indicate whether the event requires
a branch stack setup. Replace the needs_branch_stack() by checking the
new flag.

The counting event check is implemented here. The later patch will take
the new PERF_SAMPLE_BRANCH_COUNTERS into account.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20231025201626.3000228-2-kan.liang@linux.intel.com
This commit is contained in:
Kan Liang 2023-10-25 13:16:20 -07:00 committed by Peter Zijlstra
parent 571d91dcad
commit 85846b2707
2 changed files with 12 additions and 3 deletions
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14
arch/x86/events/intel/core.c
View File

@ -2527,9 +2527,14 @@ static void intel_pmu_assign_event(struct perf_event *event, int idx)
perf_report_aux_output_id(event, idx);
}
static __always_inline bool intel_pmu_needs_branch_stack(struct perf_event *event)
{
return event->hw.flags & PERF_X86_EVENT_NEEDS_BRANCH_STACK;
}
static void intel_pmu_del_event(struct perf_event *event)
{
if (needs_branch_stack(event))
if (intel_pmu_needs_branch_stack(event))
intel_pmu_lbr_del(event);
if (event->attr.precise_ip)
intel_pmu_pebs_del(event);
@ -2820,7 +2825,7 @@ static void intel_pmu_add_event(struct perf_event *event)
{
if (event->attr.precise_ip)
intel_pmu_pebs_add(event);
if (needs_branch_stack(event))
if (intel_pmu_needs_branch_stack(event))
intel_pmu_lbr_add(event);
}
@ -3897,7 +3902,10 @@ static int intel_pmu_hw_config(struct perf_event *event)
x86_pmu.pebs_aliases(event);
}
if (needs_branch_stack(event)) {
if (needs_branch_stack(event) && is_sampling_event(event))
event->hw.flags |= PERF_X86_EVENT_NEEDS_BRANCH_STACK;
if (intel_pmu_needs_branch_stack(event)) {
ret = intel_pmu_setup_lbr_filter(event);
if (ret)
return ret;

1
arch/x86/events/perf_event_flags.h
View File

@ -20,3 +20,4 @@ PERF_ARCH(TOPDOWN, 0x04000) /* Count Topdown slots/metrics events */
PERF_ARCH(PEBS_STLAT, 0x08000) /* st+stlat data address sampling */
PERF_ARCH(AMD_BRS, 0x10000) /* AMD Branch Sampling */
PERF_ARCH(PEBS_LAT_HYBRID, 0x20000) /* ld and st lat for hybrid */
PERF_ARCH(NEEDS_BRANCH_STACK, 0x40000) /* require branch stack setup */