linux-kernel - Re: [PATCH 2/4] perf: Add filter_match() as a parameter for pinned/flexible_sched

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Message-ID: <20190429151225.GC2182@lakrids.cambridge.arm.com>
Date:   Mon, 29 Apr 2019 16:12:26 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     kan.liang@...ux.intel.com
Cc:     peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com,
        linux-kernel@...r.kernel.org, eranian@...gle.com, tj@...nel.org,
        ak@...ux.intel.com
Subject: Re: [PATCH 2/4] perf: Add filter_match() as a parameter for
 pinned/flexible_sched_in()

On Mon, Apr 29, 2019 at 07:44:03AM -0700, kan.liang@...ux.intel.com wrote:
> From: Kan Liang <kan.liang@...ux.intel.com>
> 
> A fast path will be introduced in the following patches to speed up the
> cgroup events sched in, which only needs a simpler filter_match().
> 
> Add filter_match() as a parameter for pinned/flexible_sched_in().
> 
> No functional change.

I suspect that the cost you're trying to avoid is pmu_filter_match()
iterating over the entire group, which arm systems rely upon for correct
behaviour on big.LITTLE systems.

Is that the case?

Thanks,
Mark.

> 
> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
> ---
>  kernel/events/core.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 388dd42..782fd86 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -3251,7 +3251,8 @@ static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
>  }
>  
>  static int visit_groups_merge(struct perf_event_groups *groups, int cpu,
> -			      int (*func)(struct perf_event *, void *), void *data)
> +			      int (*func)(struct perf_event *, void *, int (*)(struct perf_event *)),
> +			      void *data)
>  {
>  	struct perf_event **evt, *evt1, *evt2;
>  	int ret;
> @@ -3271,7 +3272,7 @@ static int visit_groups_merge(struct perf_event_groups *groups, int cpu,
>  			evt = &evt2;
>  		}
>  
> -		ret = func(*evt, data);
> +		ret = func(*evt, data, event_filter_match);
>  		if (ret)
>  			return ret;
>  
> @@ -3287,7 +3288,8 @@ struct sched_in_data {
>  	int can_add_hw;
>  };
>  
> -static int pinned_sched_in(struct perf_event *event, void *data)
> +static int pinned_sched_in(struct perf_event *event, void *data,
> +			   int (*filter_match)(struct perf_event *))
>  {
>  	struct sched_in_data *sid = data;
>  
> @@ -3300,7 +3302,7 @@ static int pinned_sched_in(struct perf_event *event, void *data)
>  		return 0;
>  #endif
>  
> -	if (!event_filter_match(event))
> +	if (!filter_match(event))
>  		return 0;
>  
>  	if (group_can_go_on(event, sid->cpuctx, sid->can_add_hw)) {
> @@ -3318,7 +3320,8 @@ static int pinned_sched_in(struct perf_event *event, void *data)
>  	return 0;
>  }
>  
> -static int flexible_sched_in(struct perf_event *event, void *data)
> +static int flexible_sched_in(struct perf_event *event, void *data,
> +			     int (*filter_match)(struct perf_event *))
>  {
>  	struct sched_in_data *sid = data;
>  
> @@ -3331,7 +3334,7 @@ static int flexible_sched_in(struct perf_event *event, void *data)
>  		return 0;
>  #endif
>  
> -	if (!event_filter_match(event))
> +	if (!filter_match(event))
>  		return 0;
>  
>  	if (group_can_go_on(event, sid->cpuctx, sid->can_add_hw)) {
> -- 
> 2.7.4
>