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SubjectRe: [PATCH] perf: fix symbol processing bug and greatly improve performance
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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