linux-kernel - Re: [RFC] perf tools: Add hugetlbfs memory recognition

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Message-ID: <20150630145049.GE5888@kernel.org>
Date:	Tue, 30 Jun 2015 11:50:49 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Hou Pengyang <houpengyang@...wei.com>
Cc:	mingo@...hat.com, namhyung@...nel.org, a.p.zijlstra@...llo.nl,
	wangnan0@...wei.com, linux-kernel@...r.kernel.org,
	zhu.wen-jie@...com
Subject: Re: [RFC] perf tools: Add hugetlbfs memory recognition

Em Tue, Jun 30, 2015 at 05:33:05PM +0800, Hou Pengyang escreveu:
> On 2015/6/29 21:42, Arnaldo Carvalho de Melo wrote:
> >Em Mon, Jun 29, 2015 at 10:23:29AM -0300, Arnaldo Carvalho de Melo escreveu:
> >>Em Sat, Jun 27, 2015 at 05:08:20PM +0800, Hou Pengyang escreveu:
> >>>So I wonder if there is a need to read /proc/pid/smaps instead of
> >>>/proc/pid/maps to generate MMAP2 event. Or we should solve the problem by
> >>>another way?
> >>
> >>Doing some research now...
> >
> >Bummer, seems that only smaps -> ... -> show_smap_vma_flags() will
> >expose that to userspace...
> >
> >Perhaps we can look at some global stat for HugeTLB fs to figure out if
> >we really, really need to parse smaps instead of just maps? I.e. in my
> >system, a desktop one, F21, I have:
> >
> 
> It seems no other info tell us if one process is using hugetlbfs.
> So how about an option to tell perf explicitly which file is from
> hugetlbfs, like:
> 
> ./perf report --hugetlb-file=/mnt/huge/hugepagefile
> 
> So that, we can check if a mmap area is from hugetlbfs by its name
> instead of MAP_HUGETLB.

Well, we _can_ detect this automatically, its just a matter of parsing
/proc/PID/smaps, right?

What I was discussing was a way only parse smaps when we know we need
to, i.e. when we, for instance, parsing /proc/PID/maps, find a map that
we think may be a hugetlb one, maybe some other way to tell us that
hugetlb maps are in place, looking at the hugetlbfs stats somehow?

- Arnaldo
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