Messages in this thread | | | Date | Fri, 23 Apr 2010 04:12:01 +0200 | From | Frederic Weisbecker <> | Subject | Re: [RFC][PATCH 1/4] perf: core, add group scheduling transactional APIs |
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On Fri, Apr 23, 2010 at 10:08:25AM +0800, Lin Ming wrote: > On Fri, 2010-04-23 at 01:31 +0800, Frederic Weisbecker wrote: > > On Thu, Apr 22, 2010 at 03:51:02PM +0800, Lin Ming wrote: > > > 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, my mistake in the earlier > > > > email). > > > > > > > > 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). > > > > > > > > > Reviewed-by: Stephane Eranian <eranian@google.com> > > > Reviewed-by: Peter Zijlstra <peterz@infradead.org> > > > Signed-off-by: Lin Ming <ming.m.lin@intel.com> > > > --- > > > include/linux/perf_event.h | 8 +++++--- > > > kernel/perf_event.c | 29 ++++++++++++++++------------- > > > 2 files changed, 21 insertions(+), 16 deletions(-) > > > > > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > > > index ace31fb..b16cfba 100644 > > > --- a/include/linux/perf_event.h > > > +++ b/include/linux/perf_event.h > > > @@ -532,6 +532,8 @@ struct hw_perf_event { > > > > > > struct perf_event; > > > > > > +#define PERF_EVENT_TRAN_STARTED 1 > > > + > > > /** > > > * struct pmu - generic performance monitoring unit > > > */ > > > @@ -542,6 +544,9 @@ struct pmu { > > > void (*stop) (struct perf_event *event); > > > void (*read) (struct perf_event *event); > > > void (*unthrottle) (struct perf_event *event); > > > + void (*start_txn) (const struct pmu *pmu); > > > + void (*stop_txn) (const struct pmu *pmu); > > > + int (*commit_txn) (const struct pmu *pmu); > > > > > > Please add a few comments that briefly explain what these > > *_txn callbacks are supposed to mean. > > > > Unless txn is an acronym that most kernel developers are used to. > > How about below changes? > > Thanks for review. > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index b16cfba..bba4c60 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -544,9 +544,21 @@ struct pmu { > void (*stop) (struct perf_event *event); > void (*read) (struct perf_event *event); > void (*unthrottle) (struct perf_event *event); > - void (*start_txn) (const struct pmu *pmu); > - void (*stop_txn) (const struct pmu *pmu); > - int (*commit_txn) (const struct pmu *pmu); > + > + /* > + * 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 > + */ > + > + /* start group events transaction */ > + void (*start_group_trans) (const struct pmu *pmu); > + > + /* stop group events transaction */ > + void (*stop_group_trans) (const struct pmu *pmu); > + > + /* commit group events transaction */ > + int (*commit_group_trans) (const struct pmu *pmu); > };
Looks good!
Thanks.
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