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SubjectRe: [PATCH v2 1/5] perf: Add a flags parameter to pmu txn interfaces
Peter Zijlstra [peterz@infradead.org] wrote:
| On Tue, Apr 07, 2015 at 05:34:55PM -0700, Sukadev Bhattiprolu wrote:
| > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
| > index 2b62198..4dc3d70 100644
| > --- a/include/linux/perf_event.h
| > +++ b/include/linux/perf_event.h
| > @@ -240,20 +240,27 @@ struct pmu {
| > *
| > * Start the transaction, after this ->add() doesn't need to
| > * do schedulability tests.
| > + *
| > + * Optional.
| > */
| > - void (*start_txn) (struct pmu *pmu); /* optional */
| > +#define PERF_PMU_TXN_ADD 0x1 /* txn to add/schedule event on PMU */
|
| Please do not interleave these flags in the structure. Maybe place it
| near PERF_EVENT_TXN.

Ok.

|
| > + void (*start_txn) (struct pmu *pmu, int flags);
| > /*
| > * If ->start_txn() disabled the ->add() schedulability test
| > * then ->commit_txn() is required to perform one. On success
| > * the transaction is closed. On error the transaction is kept
| > * open until ->cancel_txn() is called.
| > + *
| > + * Optional.
| > */
| > - int (*commit_txn) (struct pmu *pmu); /* optional */
| > + int (*commit_txn) (struct pmu *pmu, int flags);
| > /*
| > * Will cancel the transaction, assumes ->del() is called
| > * for each successful ->add() during the transaction.
| > + *
| > + * Optional.
| > */
| > - void (*cancel_txn) (struct pmu *pmu); /* optional */
| > + void (*cancel_txn) (struct pmu *pmu, int flags);
| >
| > /*
| > * Will return the value for perf_event_mmap_page::index for this event,
|
| So (again), why also pass the flags to cancel/commit ?
|
| The transaction state _has_ to already record it, otherwise it doesn't
| know if add/read are part of one.

I had replied to your earlier mail and added a Note to this patch
description. I was hesitating making more intrusive changes to PMUs
that don't care about the new txn type.

But, I agree, it is better to go ahead and update all PMUs to save
the state and check. Will do that in the next version.

Sukadev



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