Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753040AbcD0M4J (ORCPT ); Wed, 27 Apr 2016 08:56:09 -0400 Received: from mail.kernel.org ([198.145.29.136]:36110 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752657AbcD0M4G (ORCPT ); Wed, 27 Apr 2016 08:56:06 -0400 Date: Wed, 27 Apr 2016 09:56:02 -0300 From: Arnaldo Carvalho de Melo To: Brendan Gregg Cc: Arnaldo Carvalho de Melo , Alexei Starovoitov , David Ahern , Peter Zijlstra , Frederic Weisbecker , Ingo Molnar , Adrian Hunter , Alexander Shishkin , Alexei Starovoitov , He Kuang , Jiri Olsa , Masami Hiramatsu , Milian Wolff , Namhyung Kim , Stephane Eranian , Thomas Gleixner , Vince Weaver , Wang Nan , Zefan Li , Linux Kernel Mailing List Subject: Re: [PATCH/RFC v3] perf core: Allow setting up max frame stack depth via sysctl Message-ID: <20160427125602.GN11033@kernel.org> References: <20160425215947.GA25915@ast-mbp.thefacebook.com> <20160425234138.GA16708@kernel.org> <20160426000724.GA28705@ast-mbp.thefacebook.com> <20160426002928.GB16708@kernel.org> <20160426004358.GA29875@ast-mbp.thefacebook.com> <20160426004747.GC16708@kernel.org> <20160426210500.GK11033@kernel.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/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2224 Lines: 56 Em Tue, Apr 26, 2016 at 02:58:41PM -0700, Brendan Gregg escreveu: > On Tue, Apr 26, 2016 at 2:05 PM, Arnaldo Carvalho de Melo > wrote: > > Em Tue, Apr 26, 2016 at 01:02:34PM -0700, Brendan Gregg escreveu: > >> On Mon, Apr 25, 2016 at 5:49 PM, Brendan Gregg wrote: > >> > On Mon, Apr 25, 2016 at 5:47 PM, Arnaldo Carvalho de Melo wrote: > >> >> Em Mon, Apr 25, 2016 at 05:44:00PM -0700, Alexei Starovoitov escreveu: > >> >>> yep :) > >> >>> hopefully Brendan can give it another spin. > >> >> > >> >> Agreed, and I'm calling it a day anyway, Brendan, please consider > >> >> retesting, thanks, > >> > > >> > Will do, thanks! > >> > >> Looks good. > >> > >> I started with max depth = 512, and even that was still truncated, and > >> had to profile again at 1024 to capture the full stacks. Seems to > >> generally match the flame graph I generated with V1, which made me > >> want to check that I'm running the new patch, and am: > >> > >> # grep six_hundred_forty_kb /proc/kallsyms > >> ffffffff81c431e0 d six_hundred_forty_kb > >> > >> I was mucking around and was able to get "corrupted callchain. > >> skipping..." errors, but these look to be expected -- that was > > > > Yeah, thanks for testing! > > > > And since you talked about userspace without frame pointers, have you > > played with '--call-graph lbr'? > > Not really. Isn't it only 16 levels deep max? Yeah, stoopid me :-\ > Most of our Linux is Xen guests (EC2), and I'd have to check if the > MSRs are available for LBR (perf record --call-graph lbr ... returns > "The sys_perf_event_open() syscall returned with 95 (Operation not That is because it is only accepted for PERF_TYPE_HARDWARE on x86, i.e. it retunrs EOPNOTSUPP for all the other cases, like for PERF_TYPE_SOFTWARE counters, like "cpu-clock" > supported) for event (cpu-clock).", so I'd guess not, although many > other MSRs are exposed). > > BTS seemed more promising (deeper stacks), and there's already Xen > support for it (need to boot the Xen host with vpmu=bts, preferably > vpmu=bts,arch for some PMCs as well :). Yeah, worth a look, I guess, but doesn't look like a low hanging fruit tho. - Arnaldo