Re: [PATCH] perf_events: fix bogus warn_on(_once) inperf_prepare_sample()

From: Frederic Weisbecker
Date: Thu Apr 08 2010 - 17:42:57 EST


On Thu, Apr 08, 2010 at 11:22:05PM +0200, Stephane Eranian wrote:
> On Thu, Apr 8, 2010 at 11:17 PM, Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:
> > On Thu, Apr 08, 2010 at 11:14:15PM +0200, Stephane Eranian wrote:
> >> On Thu, Apr 8, 2010 at 11:11 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> >> > On Thu, 2010-04-08 at 23:08 +0200, Stephane Eranian wrote:
> >> >>
> >> >> Are you suggesting you add some padding the PEBS raw sample you
> >> >> return as PERF_SAMPLE_RAW? Then you need to define what RAW
> >> >> actually means? Seems here, it would mean more than what the
> >> >> HW returns.
> >> >
> >> > Well, RAW doesn't mean anything much at all, its really a fugly pass
> >> > some crap around thing.
> >> >
> >> > So yeah, adding padding seems just fine.
> >> >
> >> I would rather see size as u64. Who's using raw today anyway?
> >
> >
> > The trace events. Hence the size of the size shouldn't be touched, it
> > is an ABI now.
>
> Given your alignment constraints, it seems like it was a bad choice to pick
> u32 for size to begin with.


Indeed, I'm not exactly sure how this is dealt since this is indeed u32
and the buffer requires to align to u64...

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