linux-kernel - Re: [PATCHv2 00/25] perf tool: Add support for multiple data file storage

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Date:	Mon, 9 Sep 2013 16:03:39 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	David Ahern <dsahern@...il.com>
Subject: Re: [PATCHv2 00/25] perf tool: Add support for multiple data file
 storage

On Mon, Sep 09, 2013 at 01:55:18PM +0200, Peter Zijlstra wrote:
> On Mon, Sep 09, 2013 at 01:36:41PM +0200, Jiri Olsa wrote:
> > On Mon, Sep 09, 2013 at 01:17:49PM +0200, Peter Zijlstra wrote:
> > > On Sun, Sep 01, 2013 at 12:36:11PM +0200, Jiri Olsa wrote:
> > This patchset is actually doing 3 essential things:
> >   1) adds new perf data format version (v3)
> >   2) adds class/object to handle perf data file
> >   3) adds record '-M size' option
> 
> So the -M thing is where the multiple files stuff comes from, right?
> What's the purpose of this? Why would I care how big these files get,
> surely filesystems handle 4g+ files these days.

my usage currently is to having this running during the day:
(well whenever I remember to run it.. ;-) )

  [jolsa@...va perf]$ sudo ./perf record -g -M 1m -a

and checking report when the system or app get stuck

with multiple files I can just easily (or automaticaly)
remove old ones without restarting session

> 
> > > The only reason I wanted this is so that each thread can write its own
> > > data. The current one file thing is an immense bottle-neck for big
> > > machines.
> > > 
> > 
> > I haven't considered the thread based storage yet, but I
> > think having the simplified format and centralized file
> > handling will only help.
> 
> Please do consider it now, it'd suck to have to change the file format
> thing yet again.

ook

> 
> With both per-thread and size limited your filename generation needs
> some extra bits I suppose.

yep, and probably some merging at the end

jirka
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