Messages in this thread | | | Date | Mon, 25 May 2015 09:46:07 +0200 | From | Martin Liška <> | Subject | Re: [RFC] Add --show-total-period for perf annotate |
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On 05/23/2015 06:08 AM, Andi Kleen wrote: > Martin Liška <mliska@suse.cz> writes: > >> I've been working on a new feature for perf annotate, which should be able to annotate >> instructions with total spent time (compared to percentage usage). >> >> Let's consider following use-case. You want to compare two different compilers >> on the same code base and let's assume 90% of wall-time is spent in a single function. >> Moreover, let's say that these compilers produce assembly of a totally different size. >> >> In such case, it's very useful to get an approximation of spent time on a bunch of instructions, >> which can be compared among other compilers. Otherwise, one has to somehow sum percentages and compare >> it to size of a function. > > perf diff does not handle this? Especially with the differential > profiling options it should.
It does not work if you, in my case, compare ICC and GCC, where ICC uses a different mangling scheme for fortran modules. Moreover, situation can be more complicated if a compiler performs a bit different inlining decisions.
> >>> @@ -623,6 +624,8 @@ static int __cmd_record(struct record *rec, int argc, const char **argv) >> if (!target__none(&opts->target) && !opts->initial_delay) >> perf_evlist__enable(rec->evlist); >> >> + t0 = rdclock(); >> + >> /* >> * Let the child rip >> */ >> @@ -692,6 +695,9 @@ static int __cmd_record(struct record *rec, int argc, const char **argv) >> goto out_child; >> } >> >> + t1 = rdclock(); >> + walltime_nsecs = t1 - t0; > > The walltime can be later computed by the difference of the first and > the last time stamp after sorting the events. So you don't need the new header. > > -Andi >
Good point. Can you please help me how to compute a function percentage usage in perf annotate ;) ?
Thanks, Martin
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