Messages in this thread | | | Date | Fri, 27 Sep 2013 08:29:32 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf record: mmap output file - RFC |
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* David Ahern <dsahern@gmail.com> wrote:
> On 9/26/13 11:51 AM, Jiri Olsa wrote: > >but it's still faster, since we finally get perf a chance to sleep ;-) > > > >new time: > > real 0m30.392s > > user 0m0.041s > > sys 0m0.389s > > > >old time: > > real 0m32.235s > > user 0m3.080s > > sys 0m14.444s > > > > Another data point on the performance improvement of perf itself. > Using openssl speed as a workload and perf-stat to collect > information about the perf-record process only: > > perf stat -i -- perf record -g -o /tmp/perf.data openssl speed aes > > With write(): > 158.606380 task-clock > 72 context-switches > 34 cpu-migrations > 5,400 page-faults > 336,054,007 cycles > 137,804,036 stalled-cycles-frontend > 74,505,914 stalled-cycles-backend > 474,401,639 instructions > 91,246,072 branches > 1,968,289 branch-misses > > With mmap(): > 50.314270 task-clock > 61 context-switches > 7 cpu-migrations > 3,958 page-faults > 93,585,618 cycles > 64,878,225 stalled-cycles-frontend > 41,680,427 stalled-cycles-backend > 81,552,219 instructions > 15,301,389 branches > 387,230 branch-misses > > So time, CPU cycles, instructions all drop by more than a factor of 3.
Impressive!
Btw., a perf stat bugreport: it's not clear at all that 'task-clock' is in units of milliseconds. Would be nice to print the unit as '(ms)' or so ...
For the other entries the unit is obvious (a count) - with the exception of the task-clock.
Thanks,
Ingo
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