linux-kernel - Re: [PATCH 1/2] tools, perf: Add a precise event qualifier v2

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Date:	Thu, 12 Sep 2013 19:36:17 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Andi Kleen <andi@...stfloor.org>, Vince Weaver <vince@...ter.net>,
	Andi Kleen <ak@...ux.intel.com>, acme@...radead.org,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	torvalds@...ux-foundation.org, trinity@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...il.com>
Subject: Re: [PATCH 1/2] tools, perf: Add a precise event qualifier v2

> 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@...ux.intel.com -- Speaking for myself only.
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