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While trying to get some measures from HPC with perf record, I'm getting some incoherent values, I think.

I'm using the next command to get some mesures:

perf record -T -F997 -e cache-misses:u,branch-misses:u find / -name afile

As output, there are values that decrease instead of increase. Is it possible?

As an example, here are three consecutive measures:

...

find  6775 15876.485325: branch-misses:u:     413ff0 [unknown] (/usr/bin/find)

find  6775 15876.501636: branch-misses:u:     403d8c [unknown] (/usr/bin/find)

find  6775 15876.536531: branch-misses:u:     4140a0 [unknown] (/usr/bin/find)

...

The second measure is lower than the first one. How is it possible that branch-misses decrease? Am I misinterpreting the output?

Thanks in advance.

Regards.

  • Are you looking at the value next to [unknown} – Milind Dumbare Mar 11 '15 at 11:39
  • Hi Miline. Yes I'm looking at the hex values before [unknown]. – Alberto Garcia Mar 11 '15 at 11:58
  • Aren't those the symbol addresses of binary? isnt 15876.485325 the outpu? – Milind Dumbare Mar 11 '15 at 11:59
  • I think 15876.485325 is the timestamp. isn't it? – Alberto Garcia Mar 11 '15 at 12:00
  • Since this value never changes, I think it's the PID. – Alberto Garcia Mar 11 '15 at 12:02
0

Looks like you are using perf script which gives trace of perf record or List all raw events from perf record. Try doing perf report to see the perf output numbers

Refer http://www.brendangregg.com/perf.html

  • I can not see the values with perf report either. I think like they are not being saved. – Alberto Garcia Mar 11 '15 at 12:16
  • Also tried with: perf script -f time,event,trace -i perf.data And I get: 15854.088543: cache-misses:u: 15854.088547: cache-misses:u: 15854.088553: branch-misses:u: 15854.088554: cache-misses:u: ... So it seems that the measures are not being saved. – Alberto Garcia Mar 11 '15 at 12:17
  • if you can see perf script.. you should be able to see perf report.. run perf record for longer time – Milind Dumbare Mar 11 '15 at 12:19
  • Yes, perf report works, but it only shows percentages. Perhaps I'm not using the right tool. What I'm looking for is for a list of events values in the form: Timestamp, event, value of the counter. Perf seems to output the data summarized, not like a list of events. Am I wrong? – Alberto Garcia Mar 11 '15 at 12:25

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