linux-kernel - Re: [PATCH] perf_events: fix errors path in perf_output

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Message-ID: <AANLkTilg5BipIKkqxRH3Br5oDDluu79EXCW_bNDFR8qA@mail.gmail.com>
Date:	Mon, 17 May 2010 14:23:12 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, paulus@...ba.org,
	davem@...emloft.net, acme@...radead.org,
	perfmon2-devel@...ts.sf.net, eranian@...il.com
Subject: Re: [PATCH] perf_events: fix errors path in perf_output_begin()

On Mon, May 17, 2010 at 2:09 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> 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?
>
Fine. I'll update the patch to not account for data->lost.
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