[Bug runtime/19625] New: extern @perf() counter reading support to kernel space

[Bug runtime/19625] New: extern @perf() counter reading support to kernel space

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19625

            Bug ID: 19625
           Summary: extern @perf() counter reading support to kernel space
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
          Assignee: systemtap at sourceware dot org
          Reporter: fche at redhat dot com
  Target Milestone: ---

It appears as though the upstream kernel is growing out its capabilities to
read configured performance counter values from within kernel space.  (Search
via "bpf_perf_event_read".)  This should let systemtap measure perfctr usage
between perhaps arbitrary pairs of events.

See also http://article.gmane.org/gmane.linux.kernel.perf.user/2577 for an
ebpf/perf/llvm C program that should become expressible in a dozen lines of
stap script.

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[Bug runtime/19625] extend @perf() counter reading support to kernel space

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19625

Frank Ch. Eigler <fche at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|extern @perf() counter      |extend @perf() counter
                   |reading support to kernel   |reading support to kernel
                   |space                       |space

--- Comment #1 from Frank Ch. Eigler <fche at redhat dot com> ---
See also kernel function perf_event_read_local() and pals.
It may make it possible for perf.* probes to supply a $value context variable.

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