linux-kernel - Re: [BUG] perf top: -z option does not work

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Date:	Tue, 12 Aug 2014 17:09:17 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	"mingo\@elte.hu" <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	David Ahern <dsahern@...il.com>
Subject: Re: [BUG] perf top: -z option does not work

Hi Stephane,

On Tue, 12 Aug 2014 06:44:34 +0200, Stephane Eranian wrote:
> Hi,
>
>
> My understanding is that the -z option is used to only print a profile
> since the last refresh. So if I have a refresh of 5s, then it prints the profile
> based on the samples accumulated over the last 5 seconds.

Yep, that's what I understand about the -z behavior too.

>
> The Z mode used to be available interactively. Nowadays, it seems only
> avail from the cmdline. But it does not work.

Hmm.. it seems the stdio supports 'z' key but TUI don't.

>
> I run a simple test.
> $ sudo perf top -z
>
> Then for 5s I run a cycle-burning noploop program.
> It shows up at the top. But when it terminates, the program  still stays
> at the top of the profile for a long time. This is not what I'd expect.
> The noploop line should disappear in the next couple of refreshes after
> the program has terminated.
>
> I am using tip.git and seeing the problem. But it seems, it's been there for a
> long time.
>
> Any idea what's wrong?

Looking at the code, it only zero out the annotation info but hist
entries.  I guess we need to check the flag and throw out existing
entries instead of decaying.

Also I wonder about the order of decaying - shouldn't it be decayed
before processing current entries?  It seems current code processes
current entries first and then decays...

I'll prepare patches for this soon.

Thanks,
Namhyung
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