Messages in this thread | | | Date | Thu, 9 May 2013 14:52:18 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf: fix symbol processing bug and greatly improve performance |
| |
* Jiri Olsa <jolsa@redhat.com> 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);
For a prototype line that's OK I think.
Thanks,
Ingo
| |