linux-kernel - Re: [PATCHSET 00/12] perf tools: Apply percent-limit to callchains

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Date:	Wed, 27 Jan 2016 22:21:56 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiri Olsa <jolsa@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Wang Nan <wangnan0@...wei.com>
Subject: Re: [PATCHSET 00/12] perf tools: Apply percent-limit to callchains

Hi Jiri,

On Tue, Jan 26, 2016 at 05:15:18PM +0100, Jiri Olsa wrote:
> On Wed, Jan 27, 2016 at 12:54:17AM +0900, Namhyung Kim wrote:
> 
> SNIP
> 
> > > > > > >      0.04%     0.04%  perf     [kernel.vmlinux]  [k] x86_pmu_enable              
> > > > > > >      0.04%     0.04%  perf     [kernel.vmlinux]  [k] native_apic_mem_write       
> > > > > > > 
> > > > > > 
> > > > > > What's the problem?  Now by default callchains under 0.5% (absolute)
> > > > > > will not be shown.  I think this is intended output, and we need to
> > > > > > consider changing the default percent limit.
> > > > > 
> > > > > hm, just the TUI shows +- for entries with no callchain
> > > > 
> > > > Humm, this is an old bug, never got around to try to fix it, or is this
> > > > something you were not experiencing before this patchkit from Namhyung?
> > > > 
> > > 
> > > well, there were callchains present before this patchset ;-)
> > 
> > That is because we apply percent limit to callchains now, and the
> > default is 0.5%.  Before this patchset percent limit seems not applied
> > so you saw the callchains under the limit.
> 
> I'm just saying that in TUI I see entries without callcains (which are filtered out)
> but those entries are still marked with +- ... I dont know if that's some old issue

Ah, ok.  So you don't like the spurious folded signs..

Anyway, on second thoughts, it should be checked when sorting
callchains instead of print time.  This way we can reduce the
duplicated code here and there, and it won't show spurious signs
anymore IMHO.

Looking at the source it already have the logic indeed!  But it didn't
work for some reason.  It seems that it's because we don't have hists'
total period at the time of hists__output_resort() called.  So the
min_callchain_hits always set to 0 and no limit was applied.

I'll send a fix for the problem along with others soon.

Thanks,
Namhyung