linux-kernel - Re: [PATCH 2/3] perf tools: Cache dso data file descriptor

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Message-ID: <20140507190111.GA21160@gmail.com>
Date:	Wed, 7 May 2014 21:01:11 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Namhyung Kim <namhyung@...nel.org>, linux-kernel@...r.kernel.org,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jean Pihet <jean.pihet@...aro.org>
Subject: Re: [PATCH 2/3] perf tools: Cache dso data file descriptor


* Jiri Olsa <jolsa@...hat.com> wrote:

> On Sun, Apr 27, 2014 at 11:36:35PM +0900, Namhyung Kim wrote:
> > 2014-04-17 (목), 19:39 +0200, Jiri Olsa:
> > > Keeping the data file description open for the whole life
> > > of the dso object.
> > 
> > I suspect there might be an issue for reporting very large data file
> > with this approach - like open file limit?
> 
> I've got as high as ~200 openned file descriptors for
> ~2GB data of system wide monitoring

Note that 200 open file descriptors in themselves are not a 
scalability problem on Linux, as long as perf doesn't walk them 
linearly anywhere.

I think we are reasonably fast even with a million open files in a 
singe process, or so.

Thanks,

	Ingo
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