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

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Date:	Wed, 25 Mar 2015 10:11:47 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...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


* Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> 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? [...]

Will a followup patch be written?

Thanks,

	Ingo
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