Re: [perf] howto switch from pfmon

From: Ingo Molnar
Date: Tue Jun 23 2009 - 10:52:23 EST

* Brice Goglin <Brice.Goglin@xxxxxxxx> wrote:

> Ingo Molnar wrote:
> > You can also do a profile with such events:
> >
> > perf record -f -e r1000ffe0 ./hackbench 10
> >
> > and look at it via 'perf report'.
> >
> I am not sure what the profile file contains but 'perf
> report' only shows percentages. Is there a way to get a 'perf
> stat'-like output from 'perf report'? Or maybe just have a -f
> option in 'perf stat' to send the output into a file (with the PID
> in the name).

It's not yet possible but it's a very good feature request.

> By the way, there's a typo in the description in
> tools/perf/Documentation/perf-report.txt, you want s/via perf
> report/via perf record/

thanks, fixed and pushed out. You can generally find the latest
'perf' stuff at:

> > [ Note, there's no need to specify any --follow-* flags as that is
> > implicit in 'perf'. (and you'll probably also notice that perf
> > stat is a lot faster at following fast-forking or
> > context-switching workloads than is pfmon, because it's not ptrace
> > based.) ]
> What about threads? I didn't find any way to get per-thread
> counters.
> Ideally, I'd like to be able to see no perf-related output on
> stdout/stderr at runtime, and later have a look at per-thread
> counters like 'perf stat' does at runtime.

That's not possible yet either, but makes a lot of sense.

How many threads does your workload typically run, and how do you
get their stats displayed?

Per thread info is currently available in the profile output:

perf report --sort comm,pid,symbol

But it would be nice to either extend perf report with a --stat

perf report --stat

or to extend perf stat to take an input file via -i:

perf stat -i

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