Messages in this thread | | | Subject | Re: [PATCH 1/3] perf tools: Record total sampling time | From | Namhyung Kim <> | Date | Tue, 03 Dec 2013 00:43:29 +0900 |
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2013-12-02 (월), 13:57 +0100, Ingo Molnar: > So basically, in the end I think it should be possible to have the > following behavior: > > perf record -a -e cycles sleep 1 > > perf report stat # Reports as if we ran: 'perf stat -a -e cycles sleep 1' > perf report # Reports the usual histogram > > perf report --stat # Reports the perf stat output and the histogram > > or so.
I don't think we need both of 'perf report stat' and 'perf report --stat'. At least it looks somewhat confusing to users IMHO.
For perf report stat usage, I think there's not much thing we can do for a single event - the most case. We can simple show total count and elapsed (or sampled time) for the event, but it's already in the header with this patch.
# Samples: 4K of event 'cycles' # Event count (approx.): 4087481688 # Total sampling time : 1.001260 (sec)
If an user really want to see perf stat-like output (without the usual histogram) for a recorded session, it'd be better to have 'perf record --stat' do the job (like git diff --stat) IMHO.
> > i.e. a perf.data file would by default always carry enough information > to enable the extraction of the 'perf stat' data. > > At that point visualizing it is purely report-time logic, it does not > need any record-time options. > > This would work for multi-event sampling as well, if we do: > > perf record -a -e cycles -e branches sleep 1 > > then 'perf report stat' would output the same as: > > $ perf stat -e cycles -e branches -a sleep 1 > > Performance counter stats for 'system wide': > > 34,174,518 cycles [100.00%] > 3,155,677 branches > > 1.000802852 seconds time elapsed >
Yeah, it'd be good to have same output both for perf stat and perf report --stat (or stat if you want). But I don't think it's possible to determine multiplexed counter values like perf stat does unless we use PERF_SAMPLE_READ for recoding.
> Another neat feature this kind of workflo enables is the integration > of --repeat to perf record, so something like: > > perf record --repeat 3 -a -e cycles -e branches sleep 1 > > would save 3 samples after each other, and would allow extraction of > the statistical stability of the measurement, and 'perf report stat' > would print the same result as a raw perf stat run would: > > $ perf stat --repeat 3 -e cycles -e branches -e instructions -a sleep 1 > > Performance counter stats for 'system wide' (3 runs): > > 28,975,150,642 cycles ( +- 0.43% ) [100.00%] > 10,740,235,371 branches ( +- 0.47% ) [100.00%] > 44,535,464,754 instructions # 1.54 insns per cycle ( +- 0.47% ) > > 1.005718027 seconds time elapsed ( +- 0.43% )
Yeah, but it can be used only for a new forked workload.
> > Or something like that. At that point we share reporting between perf > stat and perf report, no special ad-hoc options are needed to just > measure and report timestamps, it would all be a 'natural' side effect > of having perf stat. > > What do you think?
I think it'd be better if we can share code as much as possible. And it'd much better if we can forget about the difference in options. :)
Thanks, Namhyung
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