linux-kernel - Re: [PATCH 1/2] perf tools: Add reference timestamp to perf header

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Message-ID: <4D065CB2.7050104@cisco.com>
Date:	Mon, 13 Dec 2010 10:49:38 -0700
From:	"David S. Ahern" <daahern@...co.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] perf tools: Add reference timestamp to perf header



On 12/13/10 10:47, Peter Zijlstra wrote:
> On Mon, 2010-12-13 at 18:35 +0100, Peter Zijlstra wrote:
>>         * this CLOCK_MONOTONIC offset (for what little good that does, since
>> our clock isn't strictly sync'ed to CLOCK_MONOTONIC so we can incur
>> arbitrary drift). 
> 
> In fact, the only sane way to do that is by creating a software counter
> that represents CLOCK_MONOTONIC and sample that say once a minute (or
> more often if you want smaller drift).
> 
> 

What about creating a PERF_RECORD_TIME and generate an event when the
counter is opened? It contains a PERF_SAMPLE_TIME and say
PERF_SAMPLE_TOD (time-of-day)? We're not sending rockets to saturn; we
just need the timestamps to match other log files.

David
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