Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753954Ab2EOEu3 (ORCPT ); Tue, 15 May 2012 00:50:29 -0400 Received: from LGEMRELSE1Q.lge.com ([156.147.1.111]:47777 "EHLO LGEMRELSE1Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751337Ab2EOEu2 convert rfc822-to-8bit (ORCPT ); Tue, 15 May 2012 00:50:28 -0400 X-AuditID: 9c93016f-b7cecae000000e00-c1-4fb1e090e496 From: Namhyung Kim To: Ingo Molnar Cc: Peter Zijlstra , Linus Torvalds , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Arjan van de Ven , David Ahern , Frederic Weisbecker , Mike Galbraith , Paul Mackerras , Stephane Eranian , arnaldo.melo@gmail.com, Arnaldo Carvalho de Melo Subject: Re: [GIT PULL 0/8] Annotation weekly ponies delivery References: <1336852387-16322-1-git-send-email-acme@infradead.org> <1336994000.2443.24.camel@twins> <20120514115551.GA6479@gmail.com> <1337007985.1552.5.camel@leonhard> Date: Tue, 15 May 2012 13:48:47 +0900 In-Reply-To: <1337007985.1552.5.camel@leonhard> (Namhyung Kim's message of "Tue, 15 May 2012 00:06:25 +0900") Message-ID: <874nri1234.fsf@sejong.aot.lge.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.0.95 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1793 Lines: 49 Hi, On Tue, 15 May 2012 00:06:25 +0900, Namhyung Kim wrote: > 2012-05-14 (월), 13:55 +0200, Ingo Molnar: >> Another detail seems to be that the bug takes per-task-inherited >> profiling. Doing: >> >> perf record -a -e cycles:pp make -j64 bzImage >> >> produces the expected number of events. Without the '-a' the bug >> Linus found triggers. >> >> Similarly, 'perf top' does not trigger the bug - because it's >> using per CPU, not per task (inherited) profiling. >> > > perf_evlist__config_attrs() has this: > > if (evlist->cpus->map[0] < 0) > opts->no_inherit = true; > > meaning that per task profiling won't enable event inheritance. I don't > know why it's needed though. I found this on commit 5d2cd90922c7 ("perf evsel: Fix use of inherit"): - /* - * Don't allow mmap() of inherited per-task counters. This - * would create a performance issue due to all children writing - * to the same buffer. - * - * FIXME: - * Proper fix is not to pass 'inherit' to perf_evsel__open*, - * but a 'flags' parameter, with 'group' folded there as well, - * then introduce a PERF_O_{MMAP,GROUP,INHERIT} enum, and if - * O_MMAP is set, emit a warning if cpu < 0 and O_INHERIT is - * set. Lets go for the minimal fix first tho. - */ - evsel->attr.inherit = (cpus->map[cpu] >= 0) && inherit; Hmm.. still don't know what to do then. Thanks, Namhyung -- 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/