Re: [perfmon2] replaying PMU interrupt and context switch

[stephane e. <er...@go...>]

Corey,

Since 2.6.24, perfmon statistics are not under /sys anymore. They are
implemented via debugfs.
You need to mount a debugfs filesystem: mount -tdebugfs none /debugfs.
You'll have a perfmon
subdir in there.


On Sat, May 3, 2008 at 2:00 AM, Corey J Ashford <cja...@us...> wrote:
>
>
> Hi Stephane,
>
>  I'm attempting to look at the ovfl_intr_replay_count entry, which should be
> in /sys/devices/cpu/cpuXX/perfmon/ovfl_replay_count right?
>  Well, I don't see a 'perfmon' subdirectory of any
> /sys/devices/system/cpu/cpuXX directory, and this is after successfully
> running a number of PAPI (on perfmon2) tests.
>  Do these entries need to be enabled somehow? What am I missing?
>
>  Thanks,
>
>  - Corey
>
>  Corey Ashford
>  Software Engineer
>  IBM Linux Technology Center, Linux Toolchain
>  Beaverton, OR
>  503-578-3507
>  cja...@us...
>
>
>  per...@li... wrote on 04/25/2008 12:55:36
> PM:
>
>  > Hello everyone,
>  [snip]
>
>  > Thus, I believe they are subject the problem. It can easily be detected
> if you
>  > look at the statistics maintained by perfmon via debugfs. Perfmon
> maintains
>  > the number of times you had to replay in the ovfl_intr_replay_count
> entry.
>  > If you see a value different than zero then it means you needed replay
>  > capability. To trigger this condition you can pin multiple self-
>  > sampling threads
>  > onto the same core and have monitoring run at kernel+user+force a lot of
>  > context switches.
>  [snip]