linux-kernel - Re: [PATCH] perf: make perf.data more self-descriptive (v8)

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Message-ID: <20111205132340.GH15738@erda.amd.com>
Date:	Mon, 5 Dec 2011 14:23:40 +0100
From:	Robert Richter <robert.richter@....com>
To:	Stephane Eranian <eranian@...gle.com>
CC:	Frederic Weisbecker <fweisbec@...il.com>,
	"acme@...hat.com" <acme@...stprotocols.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"dsahern@...il.com" <dsahern@...il.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"mingo@...e.hu" <mingo@...e.hu>
Subject: Re: [PATCH] perf: make perf.data more self-descriptive (v8)

On 01.12.11 09:53:10, Stephane Eranian wrote:
> On Thu, Dec 1, 2011 at 7:15 AM, Robert Richter <robert.richter@....com> wrote:
> > I am asking this because I want to change code in a way that treats
> > all features the same, that is just to disable the feature bit on
> > failure and then continue anyway.
> >
> You need to make sure that disabling the bit is enough to still get a consistent
> file, i.e., want to undo the effect of writing the feature to the
> file. In the case
> of the meta-data features I added that was easy simply lseek() back to
> the position
> before the call. Would that be the case with TRACE_INFO?

It should be. All features can be parsed independently. Offset and
size of a feature's data block is stored in struct perf_file_section
right after the data block of perf.data (see perf_session__write_
header()). Thus, if a feature does not exist then other features can
be processed anyway.

Thanks,

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center

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