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perf: Add group scheduling transactional APIs

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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: Stephane Eranian <eranian@google.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Cc: David Miller <davem@davemloft.net>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1272002160.5707.60.camel@minggr.sh.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Lin Ming 2010-04-23 13:56:00 +08:00 committed by Ingo Molnar
parent ab608344bc
commit 6bde9b6ce0
2 changed files with 32 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
include/linux/perf_event.h
View File

@ -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 *

33
kernel/perf_event.c
View File

@ -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,
}
}
return 0;
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: