Messages in this thread | | | Date | Wed, 08 May 2013 11:44:35 -0400 | From | Waiman Long <> | Subject | Re: [PATCH] perf: fix symbol processing bug and greatly improve performance |
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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?
Regards, Longman
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