[tip: perf/core] perf: Skip pmu_ctx based on event_type

["tip-bot2 for Kan Liang" <tip-bot2@linutronix.de>]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     b825444b6179eb071e66ca3da5ac12d4dbd808d5
Gitweb:        https://git.kernel.org/tip/b825444b6179eb071e66ca3da5ac12d4dbd808d5
Author:        Kan Liang <kan.liang@linux.intel.com>
AuthorDate:    Fri, 05 Dec 2025 16:16:37 -08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 17 Dec 2025 13:31:03 +01:00

perf: Skip pmu_ctx based on event_type

To optimize the cgroup context switch, the perf_event_pmu_context
iteration skips the PMUs without cgroup events. A bool cgroup was
introduced to indicate the case. It can work, but this way is hard to
extend for other cases, e.g. skipping non-mediated PMUs. It doesn't
make sense to keep adding bool variables.

Pass the event_type instead of the specific bool variable. Check both
the event_type and related pmu_ctx variables to decide whether skipping
a PMU.

Event flags, e.g., EVENT_CGROUP, should be cleard in the ctx->is_active.
Add EVENT_FLAGS to indicate such event flags.

No functional change.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Yongwei Ma <yongwei.ma@intel.com>
Tested-by: Xudong Hao <xudong.hao@intel.com>
Link: https://patch.msgid.link/20251206001720.468579-2-seanjc@google.com
---
 kernel/events/core.c | 74 +++++++++++++++++++++++--------------------
 1 file changed, 40 insertions(+), 34 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index dad0d3d..406371c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -165,7 +165,7 @@ enum event_type_t {
 	/* see ctx_resched() for details */
 	EVENT_CPU	= 0x10,
 	EVENT_CGROUP	= 0x20,
-
+	EVENT_FLAGS	= EVENT_CGROUP,
 	/* compound helpers */
 	EVENT_ALL         = EVENT_FLEXIBLE | EVENT_PINNED,
 	EVENT_TIME_FROZEN = EVENT_TIME | EVENT_FROZEN,
@@ -779,27 +779,37 @@ do {									\
 	___p;								\
 })
 
-#define for_each_epc(_epc, _ctx, _pmu, _cgroup)				\
+static bool perf_skip_pmu_ctx(struct perf_event_pmu_context *pmu_ctx,
+			      enum event_type_t event_type)
+{
+	if ((event_type & EVENT_CGROUP) && !pmu_ctx->nr_cgroups)
+		return true;
+	return false;
+}
+
+#define for_each_epc(_epc, _ctx, _pmu, _event_type)			\
 	list_for_each_entry(_epc, &((_ctx)->pmu_ctx_list), pmu_ctx_entry) \
-		if (_cgroup && !_epc->nr_cgroups)			\
+		if (perf_skip_pmu_ctx(_epc, _event_type))		\
 			continue;					\
 		else if (_pmu && _epc->pmu != _pmu)			\
 			continue;					\
 		else
 
-static void perf_ctx_disable(struct perf_event_context *ctx, bool cgroup)
+static void perf_ctx_disable(struct perf_event_context *ctx,
+			     enum event_type_t event_type)
 {
 	struct perf_event_pmu_context *pmu_ctx;
 
-	for_each_epc(pmu_ctx, ctx, NULL, cgroup)
+	for_each_epc(pmu_ctx, ctx, NULL, event_type)
 		perf_pmu_disable(pmu_ctx->pmu);
 }
 
-static void perf_ctx_enable(struct perf_event_context *ctx, bool cgroup)
+static void perf_ctx_enable(struct perf_event_context *ctx,
+			    enum event_type_t event_type)
 {
 	struct perf_event_pmu_context *pmu_ctx;
 
-	for_each_epc(pmu_ctx, ctx, NULL, cgroup)
+	for_each_epc(pmu_ctx, ctx, NULL, event_type)
 		perf_pmu_enable(pmu_ctx->pmu);
 }
 
@@ -964,8 +974,7 @@ static void perf_cgroup_switch(struct task_struct *task)
 		return;
 
 	WARN_ON_ONCE(cpuctx->ctx.nr_cgroups == 0);
-
-	perf_ctx_disable(&cpuctx->ctx, true);
+	perf_ctx_disable(&cpuctx->ctx, EVENT_CGROUP);
 
 	ctx_sched_out(&cpuctx->ctx, NULL, EVENT_ALL|EVENT_CGROUP);
 	/*
@@ -981,7 +990,7 @@ static void perf_cgroup_switch(struct task_struct *task)
 	 */
 	ctx_sched_in(&cpuctx->ctx, NULL, EVENT_ALL|EVENT_CGROUP);
 
-	perf_ctx_enable(&cpuctx->ctx, true);
+	perf_ctx_enable(&cpuctx->ctx, EVENT_CGROUP);
 }
 
 static int perf_cgroup_ensure_storage(struct perf_event *event,
@@ -2902,11 +2911,11 @@ static void ctx_resched(struct perf_cpu_context *cpuctx,
 
 	event_type &= EVENT_ALL;
 
-	for_each_epc(epc, &cpuctx->ctx, pmu, false)
+	for_each_epc(epc, &cpuctx->ctx, pmu, 0)
 		perf_pmu_disable(epc->pmu);
 
 	if (task_ctx) {
-		for_each_epc(epc, task_ctx, pmu, false)
+		for_each_epc(epc, task_ctx, pmu, 0)
 			perf_pmu_disable(epc->pmu);
 
 		task_ctx_sched_out(task_ctx, pmu, event_type);
@@ -2926,11 +2935,11 @@ static void ctx_resched(struct perf_cpu_context *cpuctx,
 
 	perf_event_sched_in(cpuctx, task_ctx, pmu);
 
-	for_each_epc(epc, &cpuctx->ctx, pmu, false)
+	for_each_epc(epc, &cpuctx->ctx, pmu, 0)
 		perf_pmu_enable(epc->pmu);
 
 	if (task_ctx) {
-		for_each_epc(epc, task_ctx, pmu, false)
+		for_each_epc(epc, task_ctx, pmu, 0)
 			perf_pmu_enable(epc->pmu);
 	}
 }
@@ -3479,11 +3488,10 @@ static void
 ctx_sched_out(struct perf_event_context *ctx, struct pmu *pmu, enum event_type_t event_type)
 {
 	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
+	enum event_type_t active_type = event_type & ~EVENT_FLAGS;
 	struct perf_event_pmu_context *pmu_ctx;
 	int is_active = ctx->is_active;
-	bool cgroup = event_type & EVENT_CGROUP;
 
-	event_type &= ~EVENT_CGROUP;
 
 	lockdep_assert_held(&ctx->lock);
 
@@ -3514,7 +3522,7 @@ ctx_sched_out(struct perf_event_context *ctx, struct pmu *pmu, enum event_type_t
 	 * see __load_acquire() in perf_event_time_now()
 	 */
 	barrier();
-	ctx->is_active &= ~event_type;
+	ctx->is_active &= ~active_type;
 
 	if (!(ctx->is_active & EVENT_ALL)) {
 		/*
@@ -3535,7 +3543,7 @@ ctx_sched_out(struct perf_event_context *ctx, struct pmu *pmu, enum event_type_t
 
 	is_active ^= ctx->is_active; /* changed bits */
 
-	for_each_epc(pmu_ctx, ctx, pmu, cgroup)
+	for_each_epc(pmu_ctx, ctx, pmu, event_type)
 		__pmu_ctx_sched_out(pmu_ctx, is_active);
 }
 
@@ -3691,7 +3699,7 @@ perf_event_context_sched_out(struct task_struct *task, struct task_struct *next)
 		raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
 		if (context_equiv(ctx, next_ctx)) {
 
-			perf_ctx_disable(ctx, false);
+			perf_ctx_disable(ctx, 0);
 
 			/* PMIs are disabled; ctx->nr_no_switch_fast is stable. */
 			if (local_read(&ctx->nr_no_switch_fast) ||
@@ -3715,7 +3723,7 @@ perf_event_context_sched_out(struct task_struct *task, struct task_struct *next)
 
 			perf_ctx_sched_task_cb(ctx, task, false);
 
-			perf_ctx_enable(ctx, false);
+			perf_ctx_enable(ctx, 0);
 
 			/*
 			 * RCU_INIT_POINTER here is safe because we've not
@@ -3739,13 +3747,13 @@ unlock:
 
 	if (do_switch) {
 		raw_spin_lock(&ctx->lock);
-		perf_ctx_disable(ctx, false);
+		perf_ctx_disable(ctx, 0);
 
 inside_switch:
 		perf_ctx_sched_task_cb(ctx, task, false);
 		task_ctx_sched_out(ctx, NULL, EVENT_ALL);
 
-		perf_ctx_enable(ctx, false);
+		perf_ctx_enable(ctx, 0);
 		raw_spin_unlock(&ctx->lock);
 	}
 }
@@ -4054,11 +4062,9 @@ static void
 ctx_sched_in(struct perf_event_context *ctx, struct pmu *pmu, enum event_type_t event_type)
 {
 	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
+	enum event_type_t active_type = event_type & ~EVENT_FLAGS;
 	struct perf_event_pmu_context *pmu_ctx;
 	int is_active = ctx->is_active;
-	bool cgroup = event_type & EVENT_CGROUP;
-
-	event_type &= ~EVENT_CGROUP;
 
 	lockdep_assert_held(&ctx->lock);
 
@@ -4076,7 +4082,7 @@ ctx_sched_in(struct perf_event_context *ctx, struct pmu *pmu, enum event_type_t 
 		barrier();
 	}
 
-	ctx->is_active |= (event_type | EVENT_TIME);
+	ctx->is_active |= active_type | EVENT_TIME;
 	if (ctx->task) {
 		if (!(is_active & EVENT_ALL))
 			cpuctx->task_ctx = ctx;
@@ -4091,13 +4097,13 @@ ctx_sched_in(struct perf_event_context *ctx, struct pmu *pmu, enum event_type_t 
 	 * in order to give them the best chance of going on.
 	 */
 	if (is_active & EVENT_PINNED) {
-		for_each_epc(pmu_ctx, ctx, pmu, cgroup)
+		for_each_epc(pmu_ctx, ctx, pmu, event_type)
 			__pmu_ctx_sched_in(pmu_ctx, EVENT_PINNED);
 	}
 
 	/* Then walk through the lower prio flexible groups */
 	if (is_active & EVENT_FLEXIBLE) {
-		for_each_epc(pmu_ctx, ctx, pmu, cgroup)
+		for_each_epc(pmu_ctx, ctx, pmu, event_type)
 			__pmu_ctx_sched_in(pmu_ctx, EVENT_FLEXIBLE);
 	}
 }
@@ -4114,11 +4120,11 @@ static void perf_event_context_sched_in(struct task_struct *task)
 
 	if (cpuctx->task_ctx == ctx) {
 		perf_ctx_lock(cpuctx, ctx);
-		perf_ctx_disable(ctx, false);
+		perf_ctx_disable(ctx, 0);
 
 		perf_ctx_sched_task_cb(ctx, task, true);
 
-		perf_ctx_enable(ctx, false);
+		perf_ctx_enable(ctx, 0);
 		perf_ctx_unlock(cpuctx, ctx);
 		goto rcu_unlock;
 	}
@@ -4131,7 +4137,7 @@ static void perf_event_context_sched_in(struct task_struct *task)
 	if (!ctx->nr_events)
 		goto unlock;
 
-	perf_ctx_disable(ctx, false);
+	perf_ctx_disable(ctx, 0);
 	/*
 	 * We want to keep the following priority order:
 	 * cpu pinned (that don't need to move), task pinned,
@@ -4141,7 +4147,7 @@ static void perf_event_context_sched_in(struct task_struct *task)
 	 * events, no need to flip the cpuctx's events around.
 	 */
 	if (!RB_EMPTY_ROOT(&ctx->pinned_groups.tree)) {
-		perf_ctx_disable(&cpuctx->ctx, false);
+		perf_ctx_disable(&cpuctx->ctx, 0);
 		ctx_sched_out(&cpuctx->ctx, NULL, EVENT_FLEXIBLE);
 	}
 
@@ -4150,9 +4156,9 @@ static void perf_event_context_sched_in(struct task_struct *task)
 	perf_ctx_sched_task_cb(cpuctx->task_ctx, task, true);
 
 	if (!RB_EMPTY_ROOT(&ctx->pinned_groups.tree))
-		perf_ctx_enable(&cpuctx->ctx, false);
+		perf_ctx_enable(&cpuctx->ctx, 0);
 
-	perf_ctx_enable(ctx, false);
+	perf_ctx_enable(ctx, 0);
 
 unlock:
 	perf_ctx_unlock(cpuctx, ctx);