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Message-ID: <20151021012136.GA628@sejong> Date: Wed, 21 Oct 2015 10:21:36 +0900 From: Namhyung Kim <namhyung@...nel.org> To: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com> Cc: Frederic Weisbecker <fweisbec@...il.com>, Chandler Carruth <chandlerc@...il.com>, Brendan Gregg <brendan.d.gregg@...il.com>, Ingo Molnar <mingo@...nel.org>, LKML <linux-kernel@...r.kernel.org>, Adrian Hunter <adrian.hunter@...el.com>, Borislav Petkov <bp@...e.de>, David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...hat.com>, Stephane Eranian <eranian@...gle.com>, Wang Nan <wangnan0@...wei.com>, Taeung Song <treeze.taeung@...il.com> Subject: Re: [PATCH 13/16] perf callchain: Switch default to 'graph,0.5,caller' Hi Arnaldo, On Tue, Oct 20, 2015 at 03:44:04PM -0300, Arnaldo Carvalho de Melo wrote: > Em Tue, Oct 20, 2015 at 07:21:16PM +0200, Frederic Weisbecker escreveu: > > On Tue, Oct 20, 2015 at 10:06:51AM -0300, Arnaldo Carvalho de Melo wrote: > > > Em Tue, Oct 20, 2015 at 02:19:50PM +0200, Frederic Weisbecker escreveu: > > > > On Tue, Oct 20, 2015 at 09:00:34AM -0300, Arnaldo Carvalho de Melo wrote: > > > > > Em Mon, Oct 19, 2015 at 05:16:53PM -0700, Brendan Gregg escreveu: > > > > > So are you advocating different defaults, one for --stdio (callee), > > > > > another for --tui, --gtk (caller)? > > > > > > > > This is all configurable via ~/.perfconfig :-\ > > > > > > > > Indeed, finding a default that is deemed adequate for most people is, > > > > > ho-hum, difficult 8-) > > > > > > > Most uses I've seen on LKML by the past involved callee because people > > > > mostly look at the precise point where a performance issue is. > > > > > > A good chunk of that was because that was the default? > > > > I doubt it. When you need to find the culprit of a syscall of IRQ performance issue, > > you don't care much to see __libc_start_main() / main() on the top of your callchain. > > And I noticed some other shortcoming of this ordering (caller) the stack > closer to userspace in a typical perf.data with callchains (perf record > -g) can have bogus addresses (-fomit-frame-pointer) :-\ Maybe we need to add an option to ignore unresolved callchains? > > > > > IMHO changing that order is not a good idea. Unless many users complained > > > > about it. > > > > > > Perhaps there are not that many users of callchains because the default > > > is not what they're used to see? > > > > > > Motivation for the change came from a video from Chandler, that > > > resurfaced the callchain default issue, Chandler? > > > > > > Anedoctally, he tweeted about it and people seemed to like it. > > > > Well, I would prefer to hear from regular users than random twitter followers. > > I could be wrong so lets ask some users first. > > That is why I put the "anedoctaly" :-) > > > > > > Ingo, what do you think? > > > > > > What about providing a hotkey, in the tui, to toggle caller/callee > > > views, and another hotkey to save that in ~/.perfconfig so that becomes > > > the new default? > > > That means rebuilding the whole tree, it might be costly and events need to > > be processed again. > > I never tried to reimplement that with going to/from caller/caller in > mind, should do at some point, but yeah, reprocessing all entries can be > way costly. Right. Anyway it seems useful to update config dynamically. I really need to take a look at Taeung's config patchset.. > > > > In the --stdio mode we need to add a warning in the first lines, > > > something like: > > > > > > # This is caller (or callee) based, please use --callchain ... to change it > > > > > > One way or the other people will disagree, so making it easy to switch > > > to the preferred way would be nice to have? > > > > Agreed. > > I'll probably revert this change in default and provide some way to > change it dynamically, just waiting a some more time for more comments. Agreed. Thanks, Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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