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

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Message-ID: <20101213172216.GB7417@ghostprotocols.net>
Date:	Mon, 13 Dec 2010 15:22:16 -0200
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	"David S. Ahern" <daahern@...co.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

Em Mon, Dec 13, 2010 at 06:18:19PM +0100, Peter Zijlstra escreveu:
> On Mon, 2010-12-13 at 18:15 +0100, Frederic Weisbecker wrote:
> > On Mon, Dec 13, 2010 at 06:11:29PM +0100, Peter Zijlstra wrote:
> > > On Mon, 2010-12-13 at 18:09 +0100, Frederic Weisbecker wrote:
> > > > So this should be the last one to add. Something like PERF_RECORD_GEN_EVT
> > > > that has a field in its headers containing a sub-type which can be this
> > > > wall clock but can also host about everything in the future.
> > > > 
> > > > This way we don't propagate more the possible overlap with the kernel. 
> > > 
> > > I don't see why we should add more, that's going the wrong direction.
> > 
> > This must be the last one.
> 
> No, the last one already happened, you cannot postpone the last one,
> there will always be another excuse.

Did you understand the use case? How to have multiple reference times
when appending?

"last one" means adding a multiplexor, PERF_RECORD_LAST_ONE if you will,
and inside it we add new events if the need arises. Then never again we
add a PERF_RECORD_ event in userspace.

- Arnaldo
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