Re: [PATCH] s390: Add support for z13

On Tue, Oct 04 2016, Michael Petlan wrote:

> Hi Andreas,
>
> have you or anyone tested this patch and/or s390 oprofile support
> in general? I'd love to know more about the results or at least,
> if there any, what has been tested and what not + whether there
> are any known issues regarding to HW sampling on s390.

IIRC, I just performed a quick smoke test before submitting this patch;
and oprofile didn't crash.  Other than that, I don't really know what
works and what doesn't.

Some people mentioned various issues with oprofile on s390, depending on
kernel version and environment.  Since I'm currently more focused on
other projects, I haven't investigated them.  Here are some
(unconfirmed) examples:

* The --help/--usage options of operf and ocount behave strangely.
  E.g., they attempt perf_open and just emit a cryptic error message if
  that fails.  And upon success they still yield exit code 1.

* operf is showing a warning message:

    Kernel profiling is not possible with current system config.
    Set /proc/sys/kernel/kptr_restrict to 0 to collect kernel samples.

* Without the --system-wide option, operf generates all-zero statistics.

--
Andreas


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