Re: reading PMU counts with perf leader sampling and perf script

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Tue, Sep 20, 2016 at 03:19:47PM +0000, Omar Awile escreveu:
> Hi Arnaldo,
 
> Ah that’s pretty neat. I will try it out. I found perf script really
> useful to generate properly formatted CSV (after I finally understood
> how to correctly use it). This might be something worth adding as a
> feature across all perf tools (stat, report, script). I know that some
> of the tools can print something kind of CSV, but it’s still just
> kind-of and not properly formatted, which makes parsing and processing

So, can you provide specific examples of things you think are wrong so
that we can see if something can be made to improve it?

- Arnaldo

> with other scripts/libraries cumbersome.
 
> cheers,
> 
> omar
> 
> 
> On 12 September 2016 at 22:04:26, Arnaldo Carvalho de Melo (acme@kernel.org<mailto:acme@kernel.org>) wrote:
> 
> Em Fri, Sep 09, 2016 at 02:48:53PM +0000, Omar Awile escreveu:
> > Hello,
> 
> > I’ve been trying to get periodic readouts of PMU event counts using
> > perf record (similar to what perf stat -I does but with a higher
> > precision than 10ms).
> 
> > For this I thought I could use leader sampling with ref_cycles and the
> > events I am targeting.
> 
> > For example something like this:
> 
> > $ perf record -P -c 2000000 -e '{cycles,instructions,branch-misses}:S' — ./workload
> 
> > This seems to read out the sample values for the other events whenever
> > the cycle event is sampled.
> 
> > The next step would be for me to use perf script and a little python
> > script to get the event counts but I can’t seem to find a way to do
> > this. Can someone point me in the right direction?
> 
> > perf report seems to be able to read these samples but they are shown
> > only as aggregates. Also, perf script would allow me to
> > process/analyze the data myself. If this is currently not possible,
> > how would I go about adding the missing functionality in perf script?
> 
> Can you please take a look at tools/perf/scripts/python/stat-cpi.py,
> this processes hardware counters, in python, the changeset that
> introduces it:
> 
> https://git.kernel.org/cgit/linux/kernel/git/acme/linux.git/commit/?id=b8a1962d17b4e3cfdd7b7dc9ebd94affbcb4c1c5
> 
> <SNIP>
> get CPI systemwide:
> 
> $ perf stat -e cycles,instructions -a -I 1000 record sleep 3
> # time counts unit events
> 1.000158618 594,274,711 cycles (100.00%)
> 1.000158618 441,898,250 instructions
> 2.000350973 567,649,705 cycles (100.00%)
> 2.000350973 432,669,206 instructions
> 3.000559210 561,940,430 cycles (100.00%)
> 3.000559210 420,403,465 instructions
> 3.000670798 780,105 cycles (100.00%)
> 3.000670798 326,516 instructions
> 
> $ perf script -s ./scripts/python/stat-cpi.py
> 1.000159: cpu -1, thread -1 -> cpi 1.344823 (594274711/441898250)
> 2.000351: cpu -1, thread -1 -> cpi 1.311972 (567649705/432669206)
> 3.000559: cpu -1, thread -1 -> cpi 1.336669 (561940430/420403465)
> 3.000671: cpu -1, thread -1 -> cpi 2.389178 (780105/326516)
> 
> $ perf stat -e cycles,instructions -a -I 1000 record sleep 3 | perf script -s ./scripts/python/stat-cpi.py
> 1.000202: cpu -1, thread -1 -> cpi 1.035091 (940778881/908885530)
> 2.000392: cpu -1, thread -1 -> cpi 1.442600 (627493992/434974455)
> 3.000545: cpu -1, thread -1 -> cpi 1.353612 (741463930/547766890)
> 3.000622: cpu -1, thread -1 -> cpi 2.642110 (784083/296764)
> 
> <SNIP>
> 
> And that -I limitation can be lifted, no?
> 
> - Arnaldo
> --
> Omar Awile, Ph.D.
> Systems Performance Engineer
> CERN - 513/R-046