From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754615Ab1BIUM3 (ORCPT ); Wed, 9 Feb 2011 15:12:29 -0500 Received: from mail-gx0-f174.google.com ([209.85.161.174]:48514 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750720Ab1BIUM2 (ORCPT ); Wed, 9 Feb 2011 15:12:28 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; b=rIWSek4YJvmDnqZRIVvVkZiTqPobdTFUW5/lKIgI9VNkLM0/ZTaqeHGA/idPxh9e0H F2bL9wotowHzedn9jLoJvBrwgxbq5vFYItz0qiAAoE1FsXRbGDsLA1PrTv4erMN6nTxC nNNsc4b1lYCIiuZiimH5Fd+AmdfQ6wDGqUq5c= Message-ID: <4D52F526.5060101@gmail.com> Date: Wed, 09 Feb 2011 13:12:22 -0700 From: David Ahern User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc13 Thunderbird/3.1.7 MIME-Version: 1.0 To: Jeff Moyer CC: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Paul Mackerras , Arnaldo Carvalho de Melo Subject: Re: perf on 2.6.38-rc4 wedges my box References: <4D52D31E.5010801@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/09/11 11:22, Jeff Moyer wrote: > David Ahern writes: > >> Have you tried '-e cpu-clock' for S/W based profiling vs the default H/W >> profiling? Add -v to see if the fallback to S/W is happening now. > > Thanks for the suggestion, David. I tried: > > # perf record -v ls > 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) ] > > If I explicitly set '-e cpu-clock', then the output is the same, > except that the warning is gone. What's up with the /proc/-1/*? target_{pid,tid} are initialized to -1 in builtin-record.c I believe the tid version is making its way through the event__synthesize_xxx code (event__synthesize_thread -> __event__synthesize_thread -> event__synthesize_comm and event__synthesize_mmap_events). > > Now, when running perf record -e cpu-clock on the aio-stress run, > unsurprisingly, I get the same result: > > # perf record -e cpu-clock -v -- ./aio-stress -O -o 0 -r 4 -d 32 -b 16 /dev/sds > couldn't open /proc/-1/status > couldn't open /proc/-1/maps > adding stage write > starting with write > file size 1024MB, record size 4KB, depth 32, ios per iteration 8 > max io_submit 16, buffer alignment set to 4KB > threads 1 files 1 contexts 1 context offset 2MB verification off > adding file /dev/sds thread 0 > > and there it sits. In this case, however, I did not see the NOHZ > warnings on the console, and this time the machine is still responding > to ping, but nothing else. cpu-clock is handled through hrtimers if that helps understand the lockup. David > > Cheers, > Jeff