diff mbox series

[4.19,1/2] perf/cgroups: Don't rotate events for cgroups unnecessarily

Message ID 20210607075938.8840-1-wenyang@linux.alibaba.com
State New
Headers show
Series [4.19,1/2] perf/cgroups: Don't rotate events for cgroups unnecessarily | expand

Commit Message

Wen Yang June 7, 2021, 7:59 a.m. UTC 
From: Ian Rogers <irogers@google.com>

[ Upstream commit fd7d55172d1e2e501e6da0a5c1de25f06612dc2e ]

Currently perf_rotate_context assumes that if the context's nr_events !=
nr_active a rotation is necessary for perf event multiplexing. With
cgroups, nr_events is the total count of events for all cgroups and
nr_active will not include events in a cgroup other than the current
task's. This makes rotation appear necessary for cgroups when it is not.

Add a perf_event_context flag that is set when rotation is necessary.
Clear the flag during sched_out and set it when a flexible sched_in
fails due to resources.

Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lkml.kernel.org/r/20190601082722.44543-1-irogers@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org # 4.19+
Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
---
 include/linux/perf_event.h |  5 +++++
 kernel/events/core.c       | 42 ++++++++++++++++++++++--------------------
 2 files changed, 27 insertions(+), 20 deletions(-)

Comments

Wen Yang June 9, 2021, 6:28 a.m. UTC | #1 
Hi,

except for the following two patches:

fd7d55172d1e ("perf/cgroups: Don't rotate events for cgroups unnecessarily")

7fa343b7fdc4 ("perf/core: Fix corner case in perf_rotate_context()")

And this patch is also needed:

90c91dfb86d0 ("perf/core: Fix endless multiplex timer")


Would you please merge them into the 4.19 stable branch?
Thanks


--
Best wishes，
Wen


在 2021/6/7 下午3:59, Wen Yang 写道:
> From: Ian Rogers <irogers@google.com>

> 

> [ Upstream commit fd7d55172d1e2e501e6da0a5c1de25f06612dc2e ]

> 

> Currently perf_rotate_context assumes that if the context's nr_events !=

> nr_active a rotation is necessary for perf event multiplexing. With

> cgroups, nr_events is the total count of events for all cgroups and

> nr_active will not include events in a cgroup other than the current

> task's. This makes rotation appear necessary for cgroups when it is not.

> 

> Add a perf_event_context flag that is set when rotation is necessary.

> Clear the flag during sched_out and set it when a flexible sched_in

> fails due to resources.

> 

> Signed-off-by: Ian Rogers <irogers@google.com>

> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>

> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>

> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>

> Cc: Borislav Petkov <bp@alien8.de>

> Cc: Jiri Olsa <jolsa@redhat.com>

> Cc: Kan Liang <kan.liang@linux.intel.com>

> Cc: Linus Torvalds <torvalds@linux-foundation.org>

> Cc: Namhyung Kim <namhyung@kernel.org>

> Cc: Peter Zijlstra <peterz@infradead.org>

> Cc: Stephane Eranian <eranian@google.com>

> Cc: Thomas Gleixner <tglx@linutronix.de>

> Cc: Vince Weaver <vincent.weaver@maine.edu>

> Link: https://lkml.kernel.org/r/20190601082722.44543-1-irogers@google.com

> Signed-off-by: Ingo Molnar <mingo@kernel.org>

> Cc: stable@vger.kernel.org # 4.19+

> Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>

> ---

>   include/linux/perf_event.h |  5 +++++

>   kernel/events/core.c       | 42 ++++++++++++++++++++++--------------------

>   2 files changed, 27 insertions(+), 20 deletions(-)

> 

> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h

> index d8b4d31..efe30b9 100644

> --- a/include/linux/perf_event.h

> +++ b/include/linux/perf_event.h

> @@ -747,6 +747,11 @@ struct perf_event_context {

>   	int				nr_stat;

>   	int				nr_freq;

>   	int				rotate_disable;

> +	/*

> +	 * Set when nr_events != nr_active, except tolerant to events not

> +	 * necessary to be active due to scheduling constraints, such as cgroups.

> +	 */

> +	int				rotate_necessary;

>   	atomic_t			refcount;

>   	struct task_struct		*task;

>   

> diff --git a/kernel/events/core.c b/kernel/events/core.c

> index b8b74a4..56e3789 100644

> --- a/kernel/events/core.c

> +++ b/kernel/events/core.c

> @@ -2952,6 +2952,12 @@ static void ctx_sched_out(struct perf_event_context *ctx,

>   	if (!ctx->nr_active || !(is_active & EVENT_ALL))

>   		return;

>   

> +	/*

> +	 * If we had been multiplexing, no rotations are necessary, now no events

> +	 * are active.

> +	 */

> +	ctx->rotate_necessary = 0;

> +

>   	perf_pmu_disable(ctx->pmu);

>   	if (is_active & EVENT_PINNED) {

>   		list_for_each_entry_safe(event, tmp, &ctx->pinned_active, active_list)

> @@ -3319,10 +3325,13 @@ static int flexible_sched_in(struct perf_event *event, void *data)

>   		return 0;

>   

>   	if (group_can_go_on(event, sid->cpuctx, sid->can_add_hw)) {

> -		if (!group_sched_in(event, sid->cpuctx, sid->ctx))

> -			list_add_tail(&event->active_list, &sid->ctx->flexible_active);

> -		else

> +		int ret = group_sched_in(event, sid->cpuctx, sid->ctx);

> +		if (ret) {

>   			sid->can_add_hw = 0;

> +			sid->ctx->rotate_necessary = 1;

> +			return 0;

> +		}

> +		list_add_tail(&event->active_list, &sid->ctx->flexible_active);

>   	}

>   

>   	return 0;

> @@ -3690,24 +3699,17 @@ static void rotate_ctx(struct perf_event_context *ctx, struct perf_event *event)

>   static bool perf_rotate_context(struct perf_cpu_context *cpuctx)

>   {

>   	struct perf_event *cpu_event = NULL, *task_event = NULL;

> -	bool cpu_rotate = false, task_rotate = false;

> -	struct perf_event_context *ctx = NULL;

> +	struct perf_event_context *task_ctx = NULL;

> +	int cpu_rotate, task_rotate;

>   

>   	/*

>   	 * Since we run this from IRQ context, nobody can install new

>   	 * events, thus the event count values are stable.

>   	 */

>   

> -	if (cpuctx->ctx.nr_events) {

> -		if (cpuctx->ctx.nr_events != cpuctx->ctx.nr_active)

> -			cpu_rotate = true;

> -	}

> -

> -	ctx = cpuctx->task_ctx;

> -	if (ctx && ctx->nr_events) {

> -		if (ctx->nr_events != ctx->nr_active)

> -			task_rotate = true;

> -	}

> +	cpu_rotate = cpuctx->ctx.rotate_necessary;

> +	task_ctx = cpuctx->task_ctx;

> +	task_rotate = task_ctx ? task_ctx->rotate_necessary : 0;

>   

>   	if (!(cpu_rotate || task_rotate))

>   		return false;

> @@ -3716,7 +3718,7 @@ static bool perf_rotate_context(struct perf_cpu_context *cpuctx)

>   	perf_pmu_disable(cpuctx->ctx.pmu);

>   

>   	if (task_rotate)

> -		task_event = ctx_first_active(ctx);

> +		task_event = ctx_first_active(task_ctx);

>   	if (cpu_rotate)

>   		cpu_event = ctx_first_active(&cpuctx->ctx);

>   

> @@ -3724,17 +3726,17 @@ static bool perf_rotate_context(struct perf_cpu_context *cpuctx)

>   	 * As per the order given at ctx_resched() first 'pop' task flexible

>   	 * and then, if needed CPU flexible.

>   	 */

> -	if (task_event || (ctx && cpu_event))

> -		ctx_sched_out(ctx, cpuctx, EVENT_FLEXIBLE);

> +	if (task_event || (task_ctx && cpu_event))

> +		ctx_sched_out(task_ctx, cpuctx, EVENT_FLEXIBLE);

>   	if (cpu_event)

>   		cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);

>   

>   	if (task_event)

> -		rotate_ctx(ctx, task_event);

> +		rotate_ctx(task_ctx, task_event);

>   	if (cpu_event)

>   		rotate_ctx(&cpuctx->ctx, cpu_event);

>   

> -	perf_event_sched_in(cpuctx, ctx, current);

> +	perf_event_sched_in(cpuctx, task_ctx, current);

>   

>   	perf_pmu_enable(cpuctx->ctx.pmu);

>   	perf_ctx_unlock(cpuctx, cpuctx->task_ctx);

>
Greg KH June 10, 2021, 10:16 p.m. UTC | #2 
On Wed, Jun 09, 2021 at 02:28:52PM +0800, Wen Yang wrote:
> 

> Hi,

> 

> except for the following two patches:

> 

> fd7d55172d1e ("perf/cgroups: Don't rotate events for cgroups unnecessarily")

> 

> 7fa343b7fdc4 ("perf/core: Fix corner case in perf_rotate_context()")

> 

> And this patch is also needed:

> 

> 90c91dfb86d0 ("perf/core: Fix endless multiplex timer")

> 

> 

> Would you please merge them into the 4.19 stable branch?


Last one now queued up, thanks.

greg k-h
diff mbox series

Patch

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d8b4d31..efe30b9 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -747,6 +747,11 @@  struct perf_event_context {
 	int				nr_stat;
 	int				nr_freq;
 	int				rotate_disable;
+	/*
+	 * Set when nr_events != nr_active, except tolerant to events not
+	 * necessary to be active due to scheduling constraints, such as cgroups.
+	 */
+	int				rotate_necessary;
 	atomic_t			refcount;
 	struct task_struct		*task;
 
diff --git a/kernel/events/core.c b/kernel/events/core.c
index b8b74a4..56e3789 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2952,6 +2952,12 @@  static void ctx_sched_out(struct perf_event_context *ctx,
 	if (!ctx->nr_active || !(is_active & EVENT_ALL))
 		return;
 
+	/*
+	 * If we had been multiplexing, no rotations are necessary, now no events
+	 * are active.
+	 */
+	ctx->rotate_necessary = 0;
+
 	perf_pmu_disable(ctx->pmu);
 	if (is_active & EVENT_PINNED) {
 		list_for_each_entry_safe(event, tmp, &ctx->pinned_active, active_list)
@@ -3319,10 +3325,13 @@  static int flexible_sched_in(struct perf_event *event, void *data)
 		return 0;
 
 	if (group_can_go_on(event, sid->cpuctx, sid->can_add_hw)) {
-		if (!group_sched_in(event, sid->cpuctx, sid->ctx))
-			list_add_tail(&event->active_list, &sid->ctx->flexible_active);
-		else
+		int ret = group_sched_in(event, sid->cpuctx, sid->ctx);
+		if (ret) {
 			sid->can_add_hw = 0;
+			sid->ctx->rotate_necessary = 1;
+			return 0;
+		}
+		list_add_tail(&event->active_list, &sid->ctx->flexible_active);
 	}
 
 	return 0;
@@ -3690,24 +3699,17 @@  static void rotate_ctx(struct perf_event_context *ctx, struct perf_event *event)
 static bool perf_rotate_context(struct perf_cpu_context *cpuctx)
 {
 	struct perf_event *cpu_event = NULL, *task_event = NULL;
-	bool cpu_rotate = false, task_rotate = false;
-	struct perf_event_context *ctx = NULL;
+	struct perf_event_context *task_ctx = NULL;
+	int cpu_rotate, task_rotate;
 
 	/*
 	 * Since we run this from IRQ context, nobody can install new
 	 * events, thus the event count values are stable.
 	 */
 
-	if (cpuctx->ctx.nr_events) {
-		if (cpuctx->ctx.nr_events != cpuctx->ctx.nr_active)
-			cpu_rotate = true;
-	}
-
-	ctx = cpuctx->task_ctx;
-	if (ctx && ctx->nr_events) {
-		if (ctx->nr_events != ctx->nr_active)
-			task_rotate = true;
-	}
+	cpu_rotate = cpuctx->ctx.rotate_necessary;
+	task_ctx = cpuctx->task_ctx;
+	task_rotate = task_ctx ? task_ctx->rotate_necessary : 0;
 
 	if (!(cpu_rotate || task_rotate))
 		return false;
@@ -3716,7 +3718,7 @@  static bool perf_rotate_context(struct perf_cpu_context *cpuctx)
 	perf_pmu_disable(cpuctx->ctx.pmu);
 
 	if (task_rotate)
-		task_event = ctx_first_active(ctx);
+		task_event = ctx_first_active(task_ctx);
 	if (cpu_rotate)
 		cpu_event = ctx_first_active(&cpuctx->ctx);
 
@@ -3724,17 +3726,17 @@  static bool perf_rotate_context(struct perf_cpu_context *cpuctx)
 	 * As per the order given at ctx_resched() first 'pop' task flexible
 	 * and then, if needed CPU flexible.
 	 */
-	if (task_event || (ctx && cpu_event))
-		ctx_sched_out(ctx, cpuctx, EVENT_FLEXIBLE);
+	if (task_event || (task_ctx && cpu_event))
+		ctx_sched_out(task_ctx, cpuctx, EVENT_FLEXIBLE);
 	if (cpu_event)
 		cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
 
 	if (task_event)
-		rotate_ctx(ctx, task_event);
+		rotate_ctx(task_ctx, task_event);
 	if (cpu_event)
 		rotate_ctx(&cpuctx->ctx, cpu_event);
 
-	perf_event_sched_in(cpuctx, ctx, current);
+	perf_event_sched_in(cpuctx, task_ctx, current);
 
 	perf_pmu_enable(cpuctx->ctx.pmu);
 	perf_ctx_unlock(cpuctx, cpuctx->task_ctx);