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

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Message-ID: <535E6C6D.7080901@gmail.com>
Date:	Mon, 28 Apr 2014 08:57:49 -0600
From:	David Ahern <dsahern@...il.com>
To:	Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...hat.com>
CC:	linux-kernel@...r.kernel.org,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	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

On 4/28/14, 7:16 AM, Namhyung Kim wrote:
> 2014-04-28 (월), 12:01 +0200, Jiri Olsa:
>> 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
>>
>> but right that could be an issue.. I wonder we could
>> workaround this somehow, because the speed up is quite
>> noticable
>>
>> how about we monitor number of openned dso file descriptor
>> and once we cross this we close some portion of them
>>
>> or something along those lines ;-)
>
> Yeah, we'll need some way to control those eventually.

Handle EMFILE failures. Find an "old" one and close it to let the new 
one succeed.

David

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