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SubjectRe: [PATCH 1/8] perf callchain: Convert children list to rbtree
On Tue, Oct 08, 2013 at 11:03:16AM +0900, Namhyung Kim wrote:
> On Wed, 2 Oct 2013 12:18:28 +0200, Frederic Weisbecker wrote:
> > On Thu, Sep 26, 2013 at 05:58:03PM +0900, Namhyung Kim wrote:
> >> From: Namhyung Kim <namhyung.kim@lge.com>
> >>
> >> Current collapse stage has a scalability problem which can be
> >> reproduced easily with parallel kernel build. This is because it
> >> needs to traverse every children of callchain linearly during the
> >> collapse/merge stage. Convert it to rbtree reduced the overhead
> >> significantly.
> >>
> >> On my 400MB perf.data file which recorded with make -j32 kernel build:
> >>
> >> $ time perf --no-pager report --stdio > /dev/null
> >>
> >> before:
> >> real 6m22.073s
> >> user 6m18.683s
> >> sys 0m0.706s
> >>
> >> after:
> >> real 0m20.780s
> >> user 0m19.962s
> >> sys 0m0.689s
> >>
> >> During the perf report the overhead on append_chain_children went down
> >> from 96.69% to 18.16%:
> >>
> >> - 18.16% perf perf [.] append_chain_children
> >> - append_chain_children
> >> - 77.48% append_chain_children
> >> + 69.79% merge_chain_branch
> >> - 22.96% append_chain_children
> >> + 67.44% merge_chain_branch
> >> + 30.15% append_chain_children
> >> + 2.41% callchain_append
> >> + 7.25% callchain_append
> >> + 12.26% callchain_append
> >> + 10.22% merge_chain_branch
> >> + 11.58% perf perf [.] dso__find_symbol
> >> + 8.02% perf perf [.] sort__comm_cmp
> >> + 5.48% perf libc-2.17.so [.] malloc_consolidate
> >>
> >> Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> >> Cc: Jiri Olsa <jolsa@redhat.com>
> >> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> >> Link: http://lkml.kernel.org/n/tip-d9tcfow6stbrp4btvgs51y67@git.kernel.org
> >> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> >
> > Have you tested this patchset when collapsing is not used?
> > There are fair chances that this patchset does not only improve collapsing
> > but also callchain insertion in general. So it's probably a win in any case. But
> > still it would be nice to make sure that it's the case because we are getting
> > rid of collapsing anyway.
> >
> > The test that could tell us about that is to run "perf report -s sym" and compare the
> > time it takes to complete before and after this patch, because "-s sym" shouldn't
> > involve collapses.
> >
> > Sorting by anything that is not comm should do the trick in fact.
>
> Yes, I have similar result when collapsing is not used. Actually when I
> ran "perf report -s sym", the performance improves higher since it'd
> insert more callchains in a hist entry.

Great! I'll have a closer look and review on the callchain patches then. Please
resend these along the comm batch.

Thanks again!


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