linux-kernel - Re: [PATCH] perf record: Allow poll timeout to be specified

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Date:	Tue, 24 Mar 2015 18:21:20 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	David Ahern <david.ahern@...cle.com>, linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH] perf record: Allow poll timeout to be specified

Em Tue, Mar 24, 2015 at 05:12:11PM +0100, Ingo Molnar escreveu:
> * David Ahern <david.ahern@...cle.com> wrote:
> > Record currently wakes up based on watermarks to read events from 
> > the mmaps and write them out to the file. The result is a file that 
> > can have large blocks of events per mmap before a finished round 
> > event is added to the stream.  This in turn affects the quantity of 
> > events that have to be passed through the ordered events queue 
> > before results can be displayed to the user. For commands like 
> > perf-script this can lead to long unnecessarily long delays before a 
> > user gets output. Large systems (e.g, 1024 cpus) further compound 
> > this effect. I have seen instances where I have to wait 45 minutes 
> > for perf-script to process a 5GB file before any events are shown.
> > 
> > This patch adds an option to perf-record to allow a user to specify 
> > the poll timeout in msec. For example using 100 msec timeouts 
> > similar to perf-top means the mmaps are traversed much more 
> > frequently leading to a smoother analysis side.
> 
> Please tune the default value (perhaps influenced by N_PROC?) so that 
> users will get sane behavior without having to specify this option!

Isn't this a followup patch? I.e. changing the default from infinity to
some sane value?

Applying it now.

- Arnaldo
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