Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755414Ab3J2Npt (ORCPT ); Tue, 29 Oct 2013 09:45:49 -0400 Received: from merlin.infradead.org ([205.233.59.134]:49194 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752757Ab3J2Nps (ORCPT ); Tue, 29 Oct 2013 09:45:48 -0400 Date: Tue, 29 Oct 2013 14:45:36 +0100 From: Peter Zijlstra To: Will Deacon Cc: Vince Weaver , "linux-kernel@vger.kernel.org" , Ingo Molnar , Arnaldo Carvalho de Melo Subject: Re: perf: PERF_EVENT_IOC_PERIOD on ARM vs everywhere else Message-ID: <20131029134536.GD16117@laptop.programming.kicks-ass.net> References: <20131028085700.GB20218@mudshark.cambridge.arm.com> <20131029042810.GD22291@mudshark.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131029042810.GD22291@mudshark.cambridge.arm.com> 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: 2069 Lines: 42 On Tue, Oct 29, 2013 at 04:28:10AM +0000, Will Deacon wrote: > On Mon, Oct 28, 2013 at 02:07:48PM +0000, Vince Weaver wrote: > > It's also a shame this change apprently didn't hit the linux-kernel list > > as far as I can tell. I do my best to try to note all of the perf > > ABI-related changes there, but if things like this are going to start > > getting merged in architecture trees then things get that much harder > > to keep track of. > > I can CC LKML on ARM perf patches if you think it will help, but all PMU > backend patches go via their respective arch trees afaict. Just those that change user visible semantics that are shared between archs I suppose :-) > > > I don't want to be the `oddball' architecture (at least, not more than I am > > > already :), but I do find it tricky to follow the required semantics of perf > > > as opposed to `it happens to work this way', especially when so much of it > > > is buried in the various arch backends. So if somebody using the thing on > > > ARM has (what looks to me like) a valid issue, then I usually try and fix > > > it. > > > > But it was global behavior that was common on all architectures. > > > > Now any cross-platform tool like PAPI is going to have to have a mess of > > #ifdefs around every use of this ioctl, and it will only get worse if > > other architectures decide to "fix" the problem too. > > What would you like me to do to fix this for you? Moving more code out of > the backends and into the core will help maintain consistency between > architectures, but that's a huge job. We could start by making all archs do the same thing again; but yes ideally we'd move some of it into generic code. Not entirely sure how that will work out though, there's a reason its in per-arch code :/ Vince, what would you prefer to do here? -- 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/