Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757207AbZFLPVt (ORCPT ); Fri, 12 Jun 2009 11:21:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751582AbZFLPVl (ORCPT ); Fri, 12 Jun 2009 11:21:41 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:50712 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750744AbZFLPVk (ORCPT ); Fri, 12 Jun 2009 11:21:40 -0400 Date: Fri, 12 Jun 2009 17:21:34 +0200 From: Ingo Molnar To: Mike Frysinger Cc: Peter Zijlstra , Paul Mackerras , linux-kernel@vger.kernel.org Subject: Re: [PATCH] scripts/checksyscalls.sh: only whine perf_counter_open when supported Message-ID: <20090612152134.GA23483@elte.hu> References: <1244806169-12232-1-git-send-email-vapier@gentoo.org> <20090612120507.GH16044@elte.hu> <8bd0f97a0906120816w26d91530nf1e1967470beb99c@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8bd0f97a0906120816w26d91530nf1e1967470beb99c@mail.gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2107 Lines: 56 * Mike Frysinger wrote: > On Fri, Jun 12, 2009 at 08:05, Ingo Molnar wrote: > > * Mike Frysinger wrote: > >> If the port does not support HAVE_PERF_COUNTERS, then they can't > >> support the perf_counter_open syscall either. ?Rather than forcing > >> everyone to add an ignore (or suffer the warning until they get > >> around to implementing support), only whine about the syscall when > >> applicable. > > > > No, this patch is wrong - it's really easy to add support: just hook > > up the syscall. This should happen for every architecture really, so > > the warning is correct and it should not be patched out. > > > > PMU support is not required to get perfcounters support: if an > > architecture hooks up the syscall it will get generic software > > counters and the tools will work as well. > > > > Profiling falls back to a hrtimer-based sampling method - this is a > > much better fallback than oprofile's fall-back to the timer tick. > > This hrtimer based sampling is dynticks/nohz-correct and can go > > beyond HZ if the architecture supports hrtimers. > > these statements are actually incorrect. the perf counter code > explicitly requires: > - asm/perf_counter.h An empty stub suffices. > - support for atomic64 types (unless i missed something, x86 is the > only 32bit system that supports these) A wrapper suffices - should probably be librarized into lib/. > - some perf stubs (like set_perf_counter_pending() -- prototype > really should be in common perf_counters headers rather than forcing > the arch to copy & paste the exact same line) Agreed. > not that any of this is documented ... Patches are welcome :-) You are right that the requirements are not necessarily trivial for every arch - so i guess our original patch is correct. Acked-by: Ingo Molnar Ingo -- 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/