Date: Thu, 12 Sep 2013 19:36:17 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>, Vince Weaver <vince@deater.net>,
        Andi Kleen <ak@linux.intel.com>, acme@infradead.org,
        linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
        Stephane Eranian <eranian@google.com>, torvalds@linux-foundation.org,
        trinity@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Thomas Gleixner <tglx@linutronix.de>,
        =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>,
        Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@gmail.com>
Subject: Re: [PATCH 1/2] tools, perf: Add a precise event qualifier v2
Message-ID: <20130912173617.GI18242@two.firstfloor.org>
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 <20130723225150.GT6123@two.firstfloor.org>
 <20130912165733.GA23698@gmail.com>
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> Your feature to export 'precise' requirements on events looks useful to 
> me. We could implement it not by special casing it implicitly but by 
> saying that if ../format/precise contains something like:
> 
>    attr:240-241
> 
> then that's a natural extension of the config:X-Y format and should be 
> interpreted to mean mean 2 bits in the perf attr field. I.e. we could go 
> beyond the config bitfield.
> 
> Basically the whole perf_event_attr can be thought of as a 'giant 
> bitfield', in which we can specify values to export an enumerated list of 
> events from the kernel to tooling.
> 
> (Using attr:X-Y the config and config1 variants can be expressed as well, 
> as the config fields are inside the attr structure.)
> 
> The positions within the perf_attr are an ABI, so this would work pretty 
> well.

Wouldn't we need different bits for each architecture then?
32bit/64bit, some archs with weird alignment rules, maybe different for
BE/LE too?

Ok I suppose it could be somehow auto generated in asm-offsets.c,
although I'm not sure how to get a bitfield offset there.

-Andi


-- 
ak@linux.intel.com -- Speaking for myself only.
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