Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756838Ab1BJUAQ (ORCPT ); Thu, 10 Feb 2011 15:00:16 -0500 Received: from casper.infradead.org ([85.118.1.10]:40368 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753306Ab1BJUAO (ORCPT ); Thu, 10 Feb 2011 15:00:14 -0500 Date: Thu, 10 Feb 2011 18:00:00 -0200 From: Arnaldo Carvalho de Melo To: Jeff Moyer Cc: Ingo Molnar , linux-kernel@vger.kernel.org, David Ahern , Frederic Weisbecker , Mike Galbraith , Paul Mackerras , Peter Zijlstra , Stephane Eranian , Tom Zanussi Subject: Re: [PATCH 1/1] perf tools: Fix thread_map event synthesizing in top and record Message-ID: <20110210200000.GF20676@ghostprotocols.net> References: <1297363899-21466-1-git-send-email-acme@infradead.org> <1297363899-21466-2-git-send-email-acme@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.19 (2009-01-05) X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2056 Lines: 44 Em Thu, Feb 10, 2011 at 02:40:29PM -0500, Jeff Moyer escreveu: > Arnaldo Carvalho de Melo writes: > > From: Arnaldo Carvalho de Melo > > Jeff Moyer reported these messages: > > > > Warning: ... trying to fall back to cpu-clock-ticks > > > > couldn't open /proc/-1/status > > couldn't open /proc/-1/maps > > [ls output] > > [ perf record: Woken up 1 times to write data ] > > [ perf record: Captured and wrote 0.008 MB perf.data (~363 samples) ] > > > > That lead me and David Ahern to see that something was fishy on the thread > > synthesizing routines, at least for the case where the workload is started > > from 'perf record', as -1 is the default for target_tid in 'perf record --tid' > > parameter, so somehow we were trying to synthesize the PERF_RECORD_MMAP and > > PERF_RECORD_COMM events for the thread -1, a bug. > > > > So I investigated this and noticed that when we introduced support for > > recording a process and its threads using --pid some bugs were introduced and > > that the way to fix it was to instead of passing the target_tid to the event > > synthesizing routines we should better pass the thread_map that has the list of > > threads for a --pid or just the single thread for a --tid. > > Thanks for looking into this, acme. Honestly, I can't for the life of > me figure out from your description how this problem would have affected > systems. The fix makes the warnings go away, but I am still left with > the hung system I originally reported. I wasn't looking at that part, as described, I looked just at the /proc/-1/status part, that -1. I.e. the part I hack on, the tools. > So, what does this patch actually fix? And do you or others have any > interest in trying to work out why perf is hanging my system? Peter? - Arnaldo -- 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/