linux-kernel - Re: [BUG] perf top: --stdio causes continuous refresh

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Date:	Thu, 6 Feb 2014 12:07:05 -0200
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>, Jiri Olsa <jolsa@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [BUG] perf top: --stdio causes continuous refresh

Em Thu, Feb 06, 2014 at 02:58:01PM +0100, Stephane Eranian escreveu:
> On Thu, Feb 6, 2014 at 2:56 PM, Arnaldo Carvalho de Melo
> <acme@...hat.com> wrote:
> > Em Wed, Feb 05, 2014 at 10:25:09PM +0100, Stephane Eranian escreveu:
> >> If you run perf top on 3.14 but you force --stdio mode, perf top
> >> goes crazy and constantly refreshes the output.

> >> It does that with many older versions of the perf as well on 3.14.
> >> It runs fine with newt mode.

> >> Works fine with my 3.11 kernel. So something must be broken
> >> with 3.14.

> >> Can you reproduce the problem as well?

> > Not so far, using my perf/urgent branch:

> I am using tip.git. Or try 3.11, 3.10.

Tried torvalds/master, no problem, looking at what the top's screen
refresh thread does we can see:

[root@...andy ~]# trace -t 3562 -e \!write
     0.000 ( 0.000 ms):  ... [continued]: poll()) = 0 Timeout
  2031.522 (2002.480 ms): poll(ufds: 0x7fbb91596bb0, nfds: 1, timeout_msecs: 2000               ) = 0 Timeout
  4064.346 (2002.456 ms): poll(ufds: 0x7fbb91596bb0, nfds: 1, timeout_msecs: 2000               ) = 0 Timeout
^C[root@...andy ~]# 

I.e. waiting the default of:

                .delay_secs          = 2,

2 seconds between refreshes.

Checking out tip.tip, or are you suggesting to try an old perf binary, from
3.11 or 3.10 on top of a newer kernel?

- Arnaldo
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