Messages in this thread | | | Date | Wed, 21 Oct 2015 19:57:19 +0800 | From | "Wangnan (F)" <> | Subject | Re: [PATCH 13/16] perf callchain: Switch default to 'graph,0.5,caller' |
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On 2015/10/21 16:09, Namhyung Kim wrote: > Hi Frederic, > > On Tue, Oct 20, 2015 at 07:21:16PM +0200, Frederic Weisbecker wrote: >> 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. >> >>> >>>> 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. > Just a question. Do you often use --children and/or '--g caller' options?
For me, I always use --no-children. However, I think it is because I have used to --no-children and no one teach me how to utilize the additional information --children provided. In case when result of --no-children hard to explain I use Brendan's flame graph tool.
Thank you.
> I guess that for most kernel developers, --children is not that useful > as you said. But I think it can be useful for many userspace > developers and with '-g caller' it can be even more useful. :) > > When '-g caller' is used, the callchains shown in a (self) entry are > less important IMHO. However callchains in entries generated by > --children will show which functions are called by the entry (since > it's reversed!) and will be more important. > > Thanks, > Namhyung
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