Re: [PATCH RFC 00/10] counter read during perf sampling
From: Jiri Olsa
Date: Thu Sep 24 2015 - 04:19:27 EST
On Tue, Sep 22, 2015 at 10:13:33AM -0400, kan.liang@xxxxxxxxx wrote:
> From: Kan Liang <kan.liang@xxxxxxxxx>
> The patch series intends to read counter statistics with fixed frequency
> during sampling. The instant benefit is that we can read memory bandwidth
> from uncore event during cpu PMU event is sampling.
> Introduce 'C' event/group modifier. The event with this modifier
> will do counting not sampling. If a group with this modifier, only
> group leader do sampling. The counter statistics will be wrote in
> new RECORD type PERF_RECORD_COUNTER_READ and stored in perf.data.
> So perf report can present the counter statistics data accordingly.
> There may be an alternative way to get counter statistics during
> sampling by running perf record and perf stat together by script.
> But the script way have various issue and complex to parses the
just a thought, but isn't the way then llow to store the data from perf stat? ;-)
and be able to merge perf.data-s from perf record and stat afterwards
> $perf record -e 'cycles,uncore_imc_1/cas_count_read/C'
> --counter-read-interval 10 -a ./tchain_edit
> [ perf record: Woken up 438 times to write data ]
> [ perf record: Captured and wrote 1.232 MB perf.data (17901 samples) ]
but if we go this way I think we should keep/allow all the options perf stat
$ perf record -e cycles stat -e 'uncore_imc_1/cas_count_read/' -I 10000 -a ./tchain_edit
with all the stat option we allow -c -F ...
and reusing existing stat code
> $perf report -D
> 0x3cae0 [0x28]: PERF_RECORD_COUNTER_READ: uncore_imc_1/cas_count_read/C
> CPU 0: val 1205 ena 2046148 run 2046148
> 0x3cb08 [0x28]: PERF_RECORD_COUNTER_READ: uncore_imc_1/cas_count_read/C
> CPU 18: val 1315 ena 2001918 run 2001918
> 0x3dba0 [0x28]: PERF_RECORD_COUNTER_READ: uncore_imc_1/cas_count_read/C
> CPU 0: val 1588 ena 12191520 run 12191520
> 0x3dbc8 [0x28]: PERF_RECORD_COUNTER_READ: uncore_imc_1/cas_count_read/C
> CPU 18: val 1686 ena 12162202 run 12162202
> $perf report --stdio --socket-filter 0
> # To display the perf.data header info, please use --header/--header-only options.
> # Total Lost Samples: 0
> # Samples: 17K of event 'cycles'
> # Event count (approx.): 10119095556
> # Processor Socket: 0
> # Overhead Command Shared Object Symbol
> # ........ ............ ................... ..................................
> 97.68% tchain_edit tchain_edit [.] f3
> 0.07% tchain_edit tchain_edit [.] f2
> 0.04% swapper [kernel.vmlinux] [k] run_timer_softirq
> 0.04% swapper [kernel.vmlinux] [k] find_busiest_group
> # Samples: 0 of event 'uncore_imc_1/cas_count_read/C'
> # Event count (approx.): 0
> # Processor Socket: 0
> # uncore_imc_1/cas_count_read/C: 35937
I think we'll need special output/display for non sampling events,
something like extra window in TUI and distinguished output in stdio,
the above is hacked sampling output ;-)
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