linux-kernel - [PATCH v2 4/9] perf/x86: Add a x86_pmu::limit_period static

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Date:   Mon, 29 Aug 2022 12:10:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, kan.liang@...ux.intel.com, eranian@...gle.com,
        ravi.bangoria@....com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        acme@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        namhyung@...nel.org
Subject: [PATCH v2 4/9] perf/x86: Add a x86_pmu::limit_period static_call

Avoid a branch and indirect call.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/events/core.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -72,8 +72,9 @@ DEFINE_STATIC_CALL_NULL(x86_pmu_add,  *x
 DEFINE_STATIC_CALL_NULL(x86_pmu_del,  *x86_pmu.del);
 DEFINE_STATIC_CALL_NULL(x86_pmu_read, *x86_pmu.read);
 
-DEFINE_STATIC_CALL_NULL(x86_pmu_set_period, *x86_pmu.set_period);
-DEFINE_STATIC_CALL_NULL(x86_pmu_update,     *x86_pmu.update);
+DEFINE_STATIC_CALL_NULL(x86_pmu_set_period,   *x86_pmu.set_period);
+DEFINE_STATIC_CALL_NULL(x86_pmu_update,       *x86_pmu.update);
+DEFINE_STATIC_CALL_NULL(x86_pmu_limit_period, *x86_pmu.limit_period);
 
 DEFINE_STATIC_CALL_NULL(x86_pmu_schedule_events,       *x86_pmu.schedule_events);
 DEFINE_STATIC_CALL_NULL(x86_pmu_get_event_constraints, *x86_pmu.get_event_constraints);
@@ -1391,8 +1392,7 @@ int x86_perf_event_set_period(struct per
 	if (left > x86_pmu.max_period)
 		left = x86_pmu.max_period;
 
-	if (x86_pmu.limit_period)
-		x86_pmu.limit_period(event, &left);
+	static_call_cond(x86_pmu_limit_period)(event, &left);
 
 	this_cpu_write(pmc_prev_left[idx], left);
 
@@ -2017,6 +2017,7 @@ static void x86_pmu_static_call_update(v
 
 	static_call_update(x86_pmu_set_period, x86_pmu.set_period);
 	static_call_update(x86_pmu_update, x86_pmu.update);
+	static_call_update(x86_pmu_limit_period, x86_pmu.limit_period);
 
 	static_call_update(x86_pmu_schedule_events, x86_pmu.schedule_events);
 	static_call_update(x86_pmu_get_event_constraints, x86_pmu.get_event_constraints);