Messages in this thread | | | Date | Thu, 9 May 2013 12:19:15 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH] perf: fix symbol processing bug and greatly improve performance |
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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>
thanks, jirka
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