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Commit 6bde9b6c authored by Lin Ming's avatar Lin Ming Committed by Ingo Molnar
Browse files

perf: Add group scheduling transactional APIs 



Add group scheduling transactional APIs to struct pmu.
These APIs will be implemented in arch code, based on Peter's idea as
below.

> the idea behind hw_perf_group_sched_in() is to not perform
> schedulability tests on each event in the group, but to add the group
> as a whole and then perform one test.
>
> Of course, when that test fails, you'll have to roll-back the whole
> group again.
>
> So start_txn (or a better name) would simply toggle a flag in the pmu
> implementation that will make pmu::enable() not perform the
> schedulablilty test.
>
> Then commit_txn() will perform the schedulability test (so note the
> method has to have a !void return value.
>
> This will allow us to use the regular
> kernel/perf_event.c::group_sched_in() and all the rollback code.
> Currently each hw_perf_group_sched_in() implementation duplicates all
> the rolllback code (with various bugs).

->start_txn:
Start group events scheduling transaction, set a flag to make
pmu::enable() not perform the schedulability test, it will be performed
at commit time.

->commit_txn:
Commit group events scheduling transaction, perform the group
schedulability as a whole

->cancel_txn:
Stop group events scheduling transaction, clear the flag so
pmu::enable() will perform the schedulability test.

Reviewed-by: default avatarStephane Eranian <eranian@google.com>
Reviewed-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarLin Ming <ming.m.lin@intel.com>
Cc: David Miller <davem@davemloft.net>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1272002160.5707.60.camel@minggr.sh.intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent ab608344

include/linux/perf_event.h

+12 −3
Original line number Diff line number Diff line
@@ -547,6 +547,8 @@ struct hw_perf_event { 


struct perf_event;



#define PERF_EVENT_TXN_STARTED 1



/**

 * struct pmu - generic performance monitoring unit

 */
@@ -557,6 +559,16 @@ struct pmu { 
	void (*stop)			(struct perf_event *event);

	void (*read)			(struct perf_event *event);

	void (*unthrottle)		(struct perf_event *event);



	/*

	 * group events scheduling is treated as a transaction,

	 * add group events as a whole and perform one schedulability test.

	 * If test fails, roll back the whole group

	 */



	void (*start_txn)	(const struct pmu *pmu);

	void (*cancel_txn)	(const struct pmu *pmu);

	int  (*commit_txn)	(const struct pmu *pmu);

};



/**
@@ -823,9 +835,6 @@ extern void perf_disable(void); 
extern void perf_enable(void);

extern int perf_event_task_disable(void);

extern int perf_event_task_enable(void);

extern int hw_perf_group_sched_in(struct perf_event *group_leader,

	       struct perf_cpu_context *cpuctx,

	       struct perf_event_context *ctx);

extern void perf_event_update_userpage(struct perf_event *event);

extern int perf_event_release_kernel(struct perf_event *event);

extern struct perf_event *

kernel/perf_event.c

+20 −13
Original line number Diff line number Diff line
@@ -83,14 +83,6 @@ extern __weak const struct pmu *hw_perf_event_init(struct perf_event *event) 
void __weak hw_perf_disable(void)		{ barrier(); }

void __weak hw_perf_enable(void)		{ barrier(); }



int __weak

hw_perf_group_sched_in(struct perf_event *group_leader,

	       struct perf_cpu_context *cpuctx,

	       struct perf_event_context *ctx)

{

	return 0;

}



void __weak perf_event_print_debug(void)	{ }



static DEFINE_PER_CPU(int, perf_disable_count);
@@ -644,15 +636,20 @@ group_sched_in(struct perf_event *group_event, 
	       struct perf_cpu_context *cpuctx,

	       struct perf_event_context *ctx)

{

	struct perf_event *event, *partial_group;

	struct perf_event *event, *partial_group = NULL;

	const struct pmu *pmu = group_event->pmu;

	bool txn = false;

	int ret;



	if (group_event->state == PERF_EVENT_STATE_OFF)

		return 0;



	ret = hw_perf_group_sched_in(group_event, cpuctx, ctx);

	if (ret)

		return ret < 0 ? ret : 0;

	/* Check if group transaction availabe */

	if (pmu->start_txn)

		txn = true;



	if (txn)

		pmu->start_txn(pmu);



	if (event_sched_in(group_event, cpuctx, ctx))

		return -EAGAIN;
@@ -667,9 +664,19 @@ group_sched_in(struct perf_event *group_event, 
		}

	}



	if (txn) {

		ret = pmu->commit_txn(pmu);

		if (!ret) {

			pmu->cancel_txn(pmu);



			return 0;

		}

	}



group_error:

	if (txn)

		pmu->cancel_txn(pmu);



	/*

	 * Groups can be scheduled in as one unit only, so undo any

	 * partial group before returning: