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

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Message-ID: <1292263573.6803.381.camel@twins>
Date:	Mon, 13 Dec 2010 19:06:13 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"David S. Ahern" <daahern@...co.com>
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 Mon, 2010-12-13 at 11:01 -0700, David S. Ahern wrote:
> > Another problem with this approach is things like flight-recorder mode
> > where you constantly over-write your old data, you'd have to build some
> > trigger to always output a new record before you over-write the old one,
> > so there's always one consistent record around. Drift is an even more
> > serious problem here since flight-record more could be running for days
> > before (if ever) you dump it.
> 
> Ok. I was not aware flight-recorder mode was an option today.

You get it when you mmap the fd RO -- the only thing is you don't get a
consistent tail pointer so you have to fudge a bit.

But even if we didn't have it, we'd need a solution that would work once
we did grow it ;-)
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