[Bug runtime/17216] New: perf.hw counters misbehaviour

[Bug runtime/17216] New: perf.hw counters misbehaviour

[i.ucar86 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17216

            Bug ID: 17216
           Summary: perf.hw counters misbehaviour
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
          Assignee: systemtap at sourceware dot org
          Reporter: i.ucar86 at gmail dot com

Created attachment 7732
  --> https://sourceware.org/bugzilla/attachment.cgi?id=7732&action=edit
Two scripts that reproduce the bug

The following happens, at least, with perf.hw.instructions and
perf.hw.cpu_cycles. I think it's a runtime bug, but I'm not sure.

Check the attachment, please. It contains two files, perf_good.stp and
perf_bad.stp. They serve the same purpose: counting the number of instructions
and CPU cycles of a given executable (/usr/bin/find). And they are essentially
equal, except that the counters are declared in different order.

As one could expect, perf_good.stp prints the good result (I mean, the same as
the kernel tool "perf") while perf_bad.stp prints a bad result (specifically,
the inverse result: instructions as cycles and cycles as instructions).

How to reproduce it? The following commands do the trick (the output numbers
are fake and are provided for illustrative purposes only):

$ perf stat find /usr/bin -name "l*" -printf "%h/%f %s %Cx %Ck%CM %Y\n"
instructions: 25, cycles: 15
$ stap perf_good.stp -c "find /usr/bin -name \"l*\" -printf \"%h/%f %s %Cx
%Ck%CM %Y\n\""
instructions: 25, cycles: 15
$ stap perf_bad.stp -c "find /usr/bin -name \"l*\" -printf \"%h/%f %s %Cx
%Ck%CM %Y\n\""
instructions: 15, cycles: 25

Here is some information about my system:

$ uname -a
Linux tombstone 3.14.9-200.fc20.x86_64 #1 SMP Thu Jun 26 21:40:51 UTC 2014
x86_64 x86_64 x86_64 GNU/Linux
$ stap -V
Systemtap translator/driver (version 2.5/0.158, rpm 2.5-2.fc20)                 
Copyright (C) 2005-2014 Red Hat, Inc. and others                                
This is free software; see the source for copying conditions.                   
enabled features: AVAHI LIBRPM LIBSQLITE3 NSS BOOST_SHARED_PTR
TR1_UNORDERED_MAP NLS DYNINST JAVA LIBVIRT LIBXML2

Please, don't hesitate to ask for more information if you need.

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[Bug runtime/17216] perf.hw counters misbehaviour

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17216

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fche at redhat dot com
           Assignee|systemtap at sourceware dot org    |scox at redhat dot com

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