linux-kernel - Re: [PATCH 05/14] perf, core: allow pmu specific data for perf task context

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Date:	Wed, 5 Feb 2014 17:57:31 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	"Yan, Zheng" <zheng.z.yan@...el.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH 05/14] perf, core: allow pmu specific data for perf task context

On Fri, Jan 3, 2014 at 6:48 AM, Yan, Zheng <zheng.z.yan@...el.com> wrote:
> Later patches will use pmu specific data to save LBR stack.
>
I think the changelog could be more descriptive here.
Explain what you add.

Reviewed-by: Stephane Eranian <eranian@...gle.com>
> Signed-off-by: Yan, Zheng <zheng.z.yan@...el.com>
> ---
>  include/linux/perf_event.h |  5 +++++
>  kernel/events/core.c       | 19 ++++++++++++++++++-
>  2 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 96cb88b..147f9d3 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -252,6 +252,10 @@ struct pmu {
>          */
>         void (*sched_task)              (struct perf_event_context *ctx,
>                                          bool sched_in);
> +       /*
> +        * PMU specific data size
> +        */
> +       size_t                          task_ctx_size;
>  };
>
>  /**
> @@ -496,6 +500,7 @@ struct perf_event_context {
>         int                             pin_count;
>         int                             nr_cgroups;      /* cgroup evts */
>         int                             nr_branch_stack; /* branch_stack evt */
> +       void                            *task_ctx_data; /* pmu specific data */
>         struct rcu_head                 rcu_head;
>  };
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index aba4d6d..b6650ab 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -883,6 +883,15 @@ static void get_ctx(struct perf_event_context *ctx)
>         WARN_ON(!atomic_inc_not_zero(&ctx->refcount));
>  }
>
> +static void free_ctx(struct rcu_head *head)
> +{
> +       struct perf_event_context *ctx;
> +
> +       ctx = container_of(head, struct perf_event_context, rcu_head);
> +       kfree(ctx->task_ctx_data);
> +       kfree(ctx);
> +}
> +
>  static void put_ctx(struct perf_event_context *ctx)
>  {
>         if (atomic_dec_and_test(&ctx->refcount)) {
> @@ -890,7 +899,7 @@ static void put_ctx(struct perf_event_context *ctx)
>                         put_ctx(ctx->parent_ctx);
>                 if (ctx->task)
>                         put_task_struct(ctx->task);
> -               kfree_rcu(ctx, rcu_head);
> +               call_rcu(&ctx->rcu_head, free_ctx);
>         }
>  }
>
> @@ -3020,6 +3029,14 @@ alloc_perf_context(struct pmu *pmu, struct task_struct *task)
>         if (!ctx)
>                 return NULL;
>
> +       if (task && pmu->task_ctx_size > 0) {
> +               ctx->task_ctx_data = kzalloc(pmu->task_ctx_size, GFP_KERNEL);
> +               if (!ctx->task_ctx_data) {
> +                       kfree(ctx);
> +                       return NULL;
> +               }
> +       }
> +
>         __perf_event_init_context(ctx);
>         if (task) {
>                 ctx->task = task;
> --
> 1.8.4.2
>
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