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Subject: Re: [PATCH 02/16] perf: Add ability to attach registers dump to
 sample
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Jiri Olsa <jolsa@redhat.com>
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Date: Fri, 25 May 2012 12:01:23 +0200
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On Thu, 2012-05-24 at 13:52 +0200, Jiri Olsa wrote:
> 
> My intention was to make this general. I could just add
> bitmask for each type (user regs mask for now) but I wanted
> to be consistent with other SAMPLE_* stuff..
> 
> So current patch adds PERF_SAMPLE_REGS sample_type bit.
> Once it is set, the 'sample_regs' value is checked for what
> type of registers you want for sample.
> 
> Each type then has separate bitmask in case you want different
> registers for each type. Allowing whatever combination of regs dump
> being added to the sample, since it seems there's no firm
> decision on what combination might be needed.
> 
> Sure we can make the same with bitmasks for each regs type,
> and check the presence in sample by bitmask being not empty. 

Right, I don't know. But none of this was in the changelog.

Also, I just checked, there's architectures with more than 64 GP
registers ;-) (IA64 has 128 64bit integer registers for instance).

Now IA64 is the only one I could find, and we don't actually support
perf for it, and seeing how 'popular' IA64 is we might never, but still.