Messages in this thread | | | Date | Thu, 09 May 2013 10:46:07 -0400 | From | Waiman Long <> | Subject | Re: [PATCH] perf: fix symbol processing bug and greatly improve performance |
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On 05/09/2013 06:19 AM, Jiri Olsa wrote: > On Wed, May 08, 2013 at 11:44:35AM -0400, Waiman Long wrote: >> On 05/07/2013 05:30 AM, Jiri Olsa wrote: >>> On Mon, May 06, 2013 at 09:43:53AM -0400, Waiman Long wrote: >>>> When "perf record" was used on a large machine with a lot of CPUs, >>>> the perf post-processing time could take a lot of minutes and even >>>> hours depending on how large the resulting perf.data file was. >>>> >>>> While running AIM7 1500-user high_systime workload on a 80-core x86-64 >>>> system with a 3.9 kernel, the workload itself took about 2 minutes >>>> to run and the perf.data file had a size of 1108.746 MB. However, >>>> the post-processing step took more than 10 minutes. >>>> >>>> With a gprof-profiled perf binary, the time spent by perf was as >>>> follows: >>>> >>>> % cumulative self self total >>>> time seconds seconds calls s/call s/call name >>>> 96.90 822.10 822.10 192156 0.00 0.00 dsos__find >>>> 0.81 828.96 6.86 172089958 0.00 0.00 rb_next >>>> 0.41 832.44 3.48 48539289 0.00 0.00 rb_erase >>>> >>>> So 97% (822 seconds) of the time was spent in a single dsos_find() >>>> function. After analyzing the call-graph data below: >>>> >>>> ----------------------------------------------- >>>> 0.00 822.12 192156/192156 map__new [6] >>>> [7] 96.9 0.00 822.12 192156 vdso__dso_findnew [7] >>>> 822.10 0.00 192156/192156 dsos__find [8] >>>> 0.01 0.00 192156/192156 dsos__add [62] >>>> 0.01 0.00 192156/192366 dso__new [61] >>>> 0.00 0.00 1/45282525 memdup [31] >>>> 0.00 0.00 192156/192230 dso__set_long_name [91] >>>> ----------------------------------------------- >>>> 822.10 0.00 192156/192156 vdso__dso_findnew [7] >>>> [8] 96.9 822.10 0.00 192156 dsos__find [8] >>>> ----------------------------------------------- >>>> >>>> It was found that the vdso__dso_findnew() function failed to locate >>>> VDSO__MAP_NAME ("[vdso]") in the dso list and have to insert a new >>>> entry at the end for 192156 times. This problem is due to the fact that >>>> there are 2 types of name in the dso entry - short name and long name. >>>> The initial dso__new() adds "[vdso]" to both the short and long names. >>>> After that, vdso__dso_findnew() modifies the long name to something >>>> like /tmp/perf-vdso.so-NoXkDj. The dsos__find() function only compares >>>> the long name. As a result, the same vdso entry is duplicated many >>>> time in the dso list. This bug increases memory consumption as well >>>> as slows the symbol processing time to a crawl. >>> hi, >>> the issue is there and fix looks ok, thanks! >>> >>> though I'm not able to get vdso callchains to pop out >>> even by investigating report with vdso heavy workload. >>> >>> I'll have a closer look.. >> Is there a chance that the fix will go to v3.10 or have to wait for v3.11? > I got this from scripts/checkpatch.pl: > > WARNING: line over 80 characters > #104: FILE: tools/perf/util/dso.h:136: > +struct dso *dsos__find(struct list_head *head, const char *name, bool > cmp_short); > > otherwise it looks ok: > > Acked-by: Jiri Olsa<jolsa@redhat.com>
I am sorry that I forgot to rerun checkpatch.pl again after changing the argument type from int to bool. So I missed this warning.
I had resent an updated patch with the warning fixed. I also made some update to the patch description.
Regards, Longman
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