Re: [RFC] perf tools: Add hugetlbfs memory recognition

[Arnaldo Carvalho de Melo <acme@kernel.org>]

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