linux-kernel - Re: [PATCH] perf: make perf.data more self-descriptive (v4)

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Message-ID: <1316183832.10174.28.camel@twins>
Date:	Fri, 16 Sep 2011 16:37:12 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	David Ahern <dsahern@...il.com>, linux-kernel@...r.kernel.org,
	acme@...hat.com, mingo@...e.hu
Subject: Re: [PATCH] perf: make perf.data more self-descriptive (v4)

On Fri, 2011-09-16 at 16:35 +0200, Stephane Eranian wrote:
> On Mon, Sep 12, 2011 at 4:43 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Mon, 2011-09-12 at 16:40 +0200, Stephane Eranian wrote:
> >> I don't think this should be the test to detect endianess.
> >
> > You should be able to tell the endianness from the PERF_MAGIC string, it
> > stores the string as a u64, so depending on endianness it reads back as
> > either: PERFFILE or ELIFFREP or whatever the bswap64 result is.
> >
> 
> I believe in big endian, if you do od -c perf.data | head -1, you also see:
> 
> 0000000   P   E   R   F   F   I   L   E   h  \0  \0  \0  \0  \0  \0  \0

Sure, but all you need to know is if the file you're reading is a
different endian than your box, if it is swap stuff, if its not, you're
good.


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