[Bug runtime/15727] New: perf probes fail on rawhide

[Bug runtime/15727] New: perf probes fail on rawhide

[dsmith at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15727

            Bug ID: 15727
           Summary: perf probes fail on rawhide
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
          Assignee: systemtap at sourceware dot org
          Reporter: dsmith at redhat dot com

Perf probes on rawhide (3.11.0-0.rc0.git2.1.fc20.x86_64) fail (even when run as
root - see bug #14223).

Using the test program from systemtap.base/perf.exp:

====
/usr/local/bin/stap -ve 'probe perf.hw.cpu_cycles.process("./towers.x") {
printf("hit\n"); exit() }' -c './towers.x'
Pass 1: parsed user script and 95 library script(s) using
209712virt/27316res/3004shr/24752data kb, in 170usr/70sys/241real ms.
Pass 2: analyzed script: 1 probe(s), 1 function(s), 0 embed(s), 0 global(s)
using 210100virt/28088res/3264shr/25140data kb, in 10usr/0sys/7real ms.
Pass 3: using cached
/root/.systemtap/cache/ba/stap_ba1f187221f28cf908c6414b4a7aedc9_1217.c
Pass 4: using cached
/root/.systemtap/cache/ba/stap_ba1f187221f28cf908c6414b4a7aedc9_1217.ko
Pass 5: starting run.
WARNING: task_finder perfctr callback for task 7586 failed: -2
Pass 5: run completed in 450usr/310sys/1046real ms.
====

This causes failures in (at least) perf.exp.

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[Bug runtime/15727] perf probes fail on rawhide

[dsmith at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15727

--- Comment #1 from David Smith <dsmith at redhat dot com> ---
After lots of debugging, I've found that some of the hardware perf probe types
aren't supported, especially on intel-based systems. Verified by running
'perf':

====
# perf stat --event=cpu-cycles ./towers.x

 Performance counter stats for './towers.x':

   <not supported> cpu-cycles              

       0.233646211 seconds time elapsed
====

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[Bug runtime/15727] perf probes fail on rawhide

[dsmith at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15727

David Smith <dsmith at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from David Smith <dsmith at redhat dot com> ---
The kernel hasn't changed/improved, but stap was improved a bit by commit
76d1784.

Perf probe registration warnings now look like:

====
WARNING: perf probe
'perf.type(0).config(2).sample(1000000).process("/discer.farm/es/scratch/dsmith/systemtap/rawhide-64-2/towers.x").counter("")'
is not supported by this kernel (-2).
====

The perf.exp testcase was switched from using hardware perf probes to software
perf probes, which are more widely supported.

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