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Subject: Re: [PATCH] perf_events: fix errors path in perf_output_begin()
From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
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Date: Mon, 17 May 2010 14:09:35 +0200
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On Mon, 2010-05-17 at 14:04 +0200, Stephane Eranian wrote:
> 
> > So you want to preserve this state for when you munmap() and mmap()
> > again? The only user of data->lost is writing the PERF_RECORD_LOST
> > event, which only ever happens when you have pages, so counting it when
> > there's no pages seems futile.
> 
> You're right. But couldn't you report lost samples in the buffer header as well?

I guess you could, but what's the point? If you ask for sampling but
don't provide a buffer you don't get anything -- how's that a surprise?