Messages in this thread | | | Date | Tue, 29 Jun 2010 17:03:10 +0200 | From | Frederic Weisbecker <> | Subject | Re: [RFC][PATCH 09/11] perf: Default PMU ops |
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On Tue, Jun 29, 2010 at 04:59:51PM +0200, Peter Zijlstra wrote: > On Tue, 2010-06-29 at 16:58 +0200, Frederic Weisbecker wrote: > > On Thu, Jun 24, 2010 at 04:28:13PM +0200, Peter Zijlstra wrote: > > > Provide default implementations for the pmu txn methods, this allows > > > us to remove some conditional code. > > > > > > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > > > --- > > > kernel/perf_event.c | 48 ++++++++++++++++++++++++++++++++++++------------ > > > 1 file changed, 36 insertions(+), 12 deletions(-) > > > > > > Index: linux-2.6/kernel/perf_event.c > > > =================================================================== > > > --- linux-2.6.orig/kernel/perf_event.c > > > +++ linux-2.6/kernel/perf_event.c > > > @@ -656,21 +656,14 @@ group_sched_in(struct perf_event *group_ > > > { > > > struct perf_event *event, *partial_group = NULL; > > > struct pmu *pmu = group_event->pmu; > > > - bool txn = false; > > > > > > if (group_event->state == PERF_EVENT_STATE_OFF) > > > return 0; > > > > > > - /* Check if group transaction availabe */ > > > - if (pmu->start_txn) > > > - txn = true; > > > - > > > - if (txn) > > > - pmu->start_txn(pmu); > > > + pmu->start_txn(pmu); > > > > > > if (event_sched_in(group_event, cpuctx, ctx)) { > > > - if (txn) > > > - pmu->cancel_txn(pmu); > > > + pmu->cancel_txn(pmu); > > > return -EAGAIN; > > > } > > > > > > @@ -684,7 +677,7 @@ group_sched_in(struct perf_event *group_ > > > } > > > } > > > > > > - if (!txn || !pmu->commit_txn(pmu)) > > > + if (!pmu->commit_txn(pmu)) > > > return 0; > > > > > > group_error: > > > @@ -699,8 +692,7 @@ group_error: > > > } > > > event_sched_out(group_event, cpuctx, ctx); > > > > > > - if (txn) > > > - pmu->cancel_txn(pmu); > > > + pmu->cancel_txn(pmu); > > > > > > return -EAGAIN; > > > } > > > @@ -4755,6 +4747,26 @@ static struct list_head pmus; > > > static DEFINE_MUTEX(pmus_lock); > > > static struct srcu_struct pmus_srcu; > > > > > > +static void perf_pmu_nop(struct pmu *pmu) > > > +{ > > > +} > > > + > > > +static void perf_pmu_start_txn(struct pmu *pmu) > > > +{ > > > + perf_pmu_disable(pmu); > > > +} > > > + > > > +static int perf_pmu_commit_txn(struct pmu *pmu) > > > +{ > > > + perf_pmu_enable(pmu); > > > + return 0; > > > +} > > > + > > > +static void perf_pmu_cancel_txn(struct pmu *pmu) > > > +{ > > > + perf_pmu_enable(pmu); > > > +} > > > > > > So why do you need perf_pmu_*able wrappers now that you brings stubs > > if none is provided? > > > > Actually, one problem is that it makes calling two indirect nops > > for software events. > > > > Should the txn things really map to the enable/disable ops is the > > off-case? Probably better let pmu implementations deal with that. > > If they didn't provide txn implementations, it means they don't need it, > > hence it should directly map to a nop. > > > > You mean, if (!pmu->start_txn && pmu->pmu_enable) { /* install defaults > */ } ?
Not really. pmu_*able and txn are there for different purposes. A pmu implementation may want to provide enable/disable things but not require any txn. Or one may just not need any of those, like software events.
It should simply map to a nop if nothing is provided.
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