linux-kernel - Re: [RFC][PATCH 2/9] perf: core, remove hw_perf_event

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Date:	Mon, 10 May 2010 14:24:46 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Lin Ming <ming.m.lin@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	"eranian@...il.com" <eranian@...il.com>,
	"Gary.Mohr@...l.com" <Gary.Mohr@...l.com>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Paul Mackerras <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Paul Mundt <lethal@...ux-sh.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 2/9] perf: core, remove hw_perf_event_init

On Mon, May 10, 2010 at 05:26:35PM +0800, Lin Ming wrote:
> A new field "pmu_id" is added to struct perf_event_attr.
> 
> 2 new functions: perf_event_register_pmu, perf_event_lookup_pmu
> perf_event_register_pmu: the pmu registration facility
> perf_event_lookup_pmu: lookup the pmu via the passed in event->attr.pmu_id.
> 
> A new api pmu->init_event to replace hw_perf_event_init
> 
> Signed-off-by: Lin Ming <ming.m.lin@...el.com>
> ---
>  include/linux/perf_event.h |    9 +++++++++
>  kernel/perf_event.c        |   39 +++++++++++++++++++++++++++++++--------
>  2 files changed, 40 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 5856d3b..6246c99 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -225,6 +225,8 @@ struct perf_event_attr {
>  	__u32			bp_type;
>  	__u64			bp_addr;
>  	__u64			bp_len;
> +
> +	int			pmu_id;
>  };
>  
>  /*
> @@ -553,6 +555,9 @@ struct perf_event;
>   * struct pmu - generic performance monitoring unit
>   */
>  struct pmu {
> +	int id;
> +	struct list_head entry;
> +
>  	int (*enable)			(struct perf_event *event);
>  	void (*disable)			(struct perf_event *event);
>  	int (*start)			(struct perf_event *event);
> @@ -569,6 +574,8 @@ struct pmu {
>  	void (*start_txn)	(struct pmu *pmu);
>  	void (*cancel_txn)	(struct pmu *pmu);
>  	int  (*commit_txn)	(struct pmu *pmu);
> +
> +	int  (*init_event)	(struct perf_event *event);
>  };
>  
>  /**
> @@ -1014,6 +1021,8 @@ extern int perf_swevent_get_recursion_context(void);
>  extern void perf_swevent_put_recursion_context(int rctx);
>  extern void perf_event_enable(struct perf_event *event);
>  extern void perf_event_disable(struct perf_event *event);
> +
> +extern void perf_event_register_pmu(struct pmu *pmu);
>  #else
>  static inline void
>  perf_event_task_sched_in(struct task_struct *task)			{ }
> diff --git a/kernel/perf_event.c b/kernel/perf_event.c
> index 36baf85..f19d40e 100644
> --- a/kernel/perf_event.c
> +++ b/kernel/perf_event.c
> @@ -40,6 +40,12 @@
>   */
>  static DEFINE_PER_CPU(struct perf_cpu_context, perf_cpu_context);
>  
> +/*
> + * The list of multiple hw pmus
> + */
> +static struct list_head pmus;
> +static int pmu_id_curr;
> +
>  int perf_max_events __read_mostly = 1;
>  static int perf_reserved_percpu __read_mostly;
>  static int perf_overcommit __read_mostly = 1;
> @@ -75,11 +81,6 @@ static DEFINE_SPINLOCK(perf_resource_lock);
>  /*
>   * Architecture provided APIs - weak aliases:
>   */
> -extern __weak struct pmu *hw_perf_event_init(struct perf_event *event)
> -{
> -	return NULL;
> -}
> -
>  void __weak hw_perf_disable(void)		{ barrier(); }
>  void __weak hw_perf_enable(void)		{ barrier(); }
>  
> @@ -4670,6 +4671,19 @@ static struct pmu *sw_perf_event_init(struct perf_event *event)
>  	return pmu;
>  }
>  
> +static struct pmu *perf_event_lookup_pmu(struct perf_event *event)
> +{
> +	struct pmu *pmu;
> +	int pmu_id = event->attr.pmu_id;
> +
> +	list_for_each_entry(pmu, &pmus, entry) {
> +		if (pmu->id == pmu_id)
> +			return pmu;
> +	}
> +
> +	return NULL;
> +}
> +
>  /*
>   * Allocate and initialize a event structure
>   */
> @@ -4685,7 +4699,7 @@ perf_event_alloc(struct perf_event_attr *attr,
>  	struct pmu *pmu;
>  	struct perf_event *event;
>  	struct hw_perf_event *hwc;
> -	long err;
> +	long err = 0;
>  
>  	event = kzalloc(sizeof(*event), gfpflags);
>  	if (!event)
> @@ -4750,7 +4764,9 @@ perf_event_alloc(struct perf_event_attr *attr,
>  	case PERF_TYPE_RAW:
>  	case PERF_TYPE_HARDWARE:
>  	case PERF_TYPE_HW_CACHE:
> -		pmu = hw_perf_event_init(event);
> +		pmu = perf_event_lookup_pmu(event);
> +		if (pmu && pmu->init_event)
> +			err = pmu->init_event(event);



Having the same for software, tracepoints and breakpoints events would
be nice, so that we have a single simple path in perf_event_alloc
to initialize the event.

Thanks.

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