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Subject[PATCH V4 10/16] perf, core: simplify need branch stack check
Date
event->attr.branch_sample_type is non-zero no matter branch stack
is enabled explicitly or is enabled implicitly. we can use it to
replace intel_pmu_needs_lbr_smpl(). This avoids duplicating code
that implicitly enables the LBR.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
---
arch/x86/kernel/cpu/perf_event_intel.c | 20 +++-----------------
include/linux/perf_event.h | 5 +++++
kernel/events/core.c | 3 +++
3 files changed, 11 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index af91bfd..a14489b 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1029,20 +1029,6 @@ static __initconst const u64 slm_hw_cache_event_ids
},
};

-static inline bool intel_pmu_needs_lbr_smpl(struct perf_event *event)
-{
- /* user explicitly requested branch sampling */
- if (has_branch_stack(event))
- return true;
-
- /* implicit branch sampling to correct PEBS skid */
- if (x86_pmu.intel_cap.pebs_trap && event->attr.precise_ip > 1 &&
- x86_pmu.intel_cap.pebs_format < 2)
- return true;
-
- return false;
-}
-
static void intel_pmu_disable_all(void)
{
struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
@@ -1207,7 +1193,7 @@ static void intel_pmu_disable_event(struct perf_event *event)
* must disable before any actual event
* because any event may be combined with LBR
*/
- if (intel_pmu_needs_lbr_smpl(event))
+ if (needs_branch_stack(event))
intel_pmu_lbr_disable(event);

if (unlikely(hwc->config_base == MSR_ARCH_PERFMON_FIXED_CTR_CTRL)) {
@@ -1268,7 +1254,7 @@ static void intel_pmu_enable_event(struct perf_event *event)
* must enabled before any actual event
* because any event may be combined with LBR
*/
- if (intel_pmu_needs_lbr_smpl(event))
+ if (needs_branch_stack(event))
intel_pmu_lbr_enable(event);

if (event->attr.exclude_host)
@@ -1738,7 +1724,7 @@ static int intel_pmu_hw_config(struct perf_event *event)
if (event->attr.precise_ip && x86_pmu.pebs_aliases)
x86_pmu.pebs_aliases(event);

- if (intel_pmu_needs_lbr_smpl(event)) {
+ if (needs_branch_stack(event)) {
ret = intel_pmu_setup_lbr_filter(event);
if (ret)
return ret;
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 7aa4794..2bf2cb2a 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -777,6 +777,11 @@ static inline bool has_branch_stack(struct perf_event *event)
return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK;
}

+static inline bool needs_branch_stack(struct perf_event *event)
+{
+ return event->attr.branch_sample_type != 0;
+}
+
extern int perf_output_begin(struct perf_output_handle *handle,
struct perf_event *event, unsigned int size);
extern void perf_output_end(struct perf_output_handle *handle);
diff --git a/kernel/events/core.c b/kernel/events/core.c
index a856813..73a6e77 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6850,6 +6850,9 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP))
goto err_ns;

+ if (!has_branch_stack(event))
+ event->attr.branch_sample_type = 0;
+
pmu = perf_init_event(event);
if (!pmu)
goto err_ns;
--
1.9.0


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