lkml.org 
[lkml]   [2015]   [Mar]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] perf tool: Fix ppid for synthesized fork events
On 3/25/15 1:15 PM, Don Zickus wrote:
> On Wed, Mar 25, 2015 at 10:51:10AM -0600, David Ahern wrote:
>> 363b785f38 added synthesized fork events and set a thread's parent id
>> to itself. Since we are already processing /proc/<pid>/status the ppid
>> can be determined properly. Make it so.
>>
>> Performance impact measured on a sparc based T5-8 (1024 CPUs):
>> $ ps -efL | wc -l
>> 20185
>>
>> Current code:
>> $ time perf record -o perf-no-ppid.data -e cpu-clock -F 1000 -a -v -BN -- usleep 1
>> mmap size 532480B
>> [ perf record: Woken up 0 times to write data ]
>> failed to write feature 9
>> [ perf record: Captured and wrote 0.000 MB perf-no-ppid.data ]
>>
>> real 0m26.144s
>> user 0m0.452s
>> sys 0m25.564s
>>
>> With PPID patch:
>> $ time ./perf_ppid record -o perf-ppid.data -e cpu-clock -F 1000 -a -v -BN -- usleep 1
>> mmap size 532480B
>> [ perf record: Woken up 0 times to write data ]
>> failed to write feature 9
>> [ perf record: Captured and wrote 0.000 MB perf-ppid.data ]
>>
>> real 0m25.743s
>> user 0m0.268s
>> sys 0m25.368s
>>
>> Signed-off-by: David Ahern <dsahern@gmail.com>
>> Cc: Don Zickus <dzickus@redhat.com>
>> Cc: Joe Mario <jmario@redhat.com>
>> Cc: Jiri Olsa <jolsa@redhat.com>
>> ---
>> v2:
>> - removed loop in place of 1 read and processing a buffer
>
> Hmm, I am not entirely sure this is correct. You made an optimization that
> hides the negative impact your patch does. I would prefer you split this
> patch into two pieces. One with the read loop optimization (which I think
> is great) and the second is your ppid change.
>
> I would then like to redo our test with the first patch applied and then
> both patches applied.
>

From your other response I take it you understand the patch now? It is
a matter of semantics to break this single into 2 -- optimize the
existing code and then add the ppid. End result will be what this patch
shows. Before I do that can you /Joe confirm the performance is acceptable?

Thanks,



\
 
 \ /
  Last update: 2015-03-25 21:01    [W:0.085 / U:0.084 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site