Hi Ingo,
On Sat, 14 Sep 2013 08:11:49 +0200, Ingo Molnar wrote:
> * Frederic Weisbecker <fweis...@gmail.com> wrote:
>> My patches and Namhyung's should improve the comm situation a lot but we
>> can't do much miracle. The only way would be perhaps to be able to limit
>> the deepness of the callchain branches.
>>
>> Now may be we can find other big contention point in perf. It's possible
>> we also have some endless loop somewhere.
>
> Well, it was the 100,000+ step linear list walk that was causing 90% of
> the slowness here. Namhyung's patch should dramatically improve that. I
> guess time for someone to post a combined tree so that it can be tested
> all together?
I pushed combined tree to 'perf/callchain-v2' branch in my tree
git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
Please note that I also pushed other versions (v[1-3]). The v1 is my
previous rbtree conversion patch, v2 adds Frederic's new comm
infrastructure series on top and v3 adds my revised patch to refer
current comm [1] on top of v2.
I did my own test again among them. Test data is 400MB perf.data file
created by parallel kernel build.
$ ls -lh perf.data.big
-rw-------. 1 namhyung namhyung 400M Sep 9 10:21 perf.data.big
For more precise result, I changed cpufreq governor to 'performance'
# echo performance > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor
and run perf report on the cpu.
$ taskset -c 3 time -p perf --no-pager report --stdio -i perf.data.big >
/dev/null
I ran it multiple times for each case and the results did not vary much.
baseline v1 v2 v3
----------------------------------------------------------
real 380.17 12.63 10.02 9.03
user 378.86 11.95 9.66 8.69
sys 0.70 0.65 0.33 0.34
I also tried to cache latest result and reuse it when adding a callchain
(in callchain_append() function) but it only hits ~5% and did not help
the performance.
Thanks,
Namhyung
[1] https://lkml.org/lkml/2013/9/16/565
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