Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754693Ab3IMI5V (ORCPT ); Fri, 13 Sep 2013 04:57:21 -0400 Received: from merlin.infradead.org ([205.233.59.134]:41731 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751487Ab3IMI5Q (ORCPT ); Fri, 13 Sep 2013 04:57:16 -0400 Date: Fri, 13 Sep 2013 10:56:54 +0200 From: Peter Zijlstra To: Andi Kleen Cc: Ingo Molnar , Vince Weaver , Andi Kleen , acme@infradead.org, linux-kernel@vger.kernel.org, Stephane Eranian , torvalds@linux-foundation.org, trinity@vger.kernel.org, Thomas Gleixner , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Jiri Olsa , Namhyung Kim Subject: Re: [PATCH 1/2] tools, perf: Add a precise event qualifier v2 Message-ID: <20130913085654.GI31370@twins.programming.kicks-ass.net> References: <1374501138-13496-1-git-send-email-andi@firstfloor.org> <20130723060108.GA18396@tassilo.jf.intel.com> <20130723225150.GT6123@two.firstfloor.org> <20130912165733.GA23698@gmail.com> <20130912173617.GI18242@two.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130912173617.GI18242@two.firstfloor.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2176 Lines: 51 On Thu, Sep 12, 2013 at 07:36:17PM +0200, Andi Kleen wrote: > > 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 Since we currently have the pattern $name:bits to mean perf_event_attr::$name the above would imply and create a possible collision with perf_event_attr::attr. If we're going to do this I'd propose using something like _:240-241, for while '_' is a valid name in C its not something we're ever going to allow in perf_event_attr. > > 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? Typically PMU drivers are per arch and all the format stuff is per pmu driver so I'd not worry about that just yet. But yes, while the perf_event_attr thing is ABI its not identical across archs. > 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. Yes, that is an unfortunate situation. I (and either Acme or Jolsa) tried wrapping the bitfield in an anonymous union to create a named variable for the entire u64 but older GCC completely fails with that. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/