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[Bug runtime/15912] on rawhide, we're getting perf probe read errors
- From: "wcohen at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sourceware dot org
- Date: Wed, 15 Jan 2014 15:50:42 +0000
- Subject: [Bug runtime/15912] on rawhide, we're getting perf probe read errors
- Auto-submitted: auto-generated
- References: <bug-15912-6586 at http dot sourceware dot org/bugzilla/>
https://sourceware.org/bugzilla/show_bug.cgi?id=15912
William Cohen <wcohen at redhat dot com> changed:
What |Removed |Added
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CC| |wcohen at redhat dot com
--- Comment #3 from William Cohen <wcohen at redhat dot com> ---
RHEL6 machines don't seem to make the performance counters available to guests.
However, for newer versions of Fedora running as the host it is possible to
use the performance counters in a guest. When the guest VM is shutdown in
libvirt. View->Details for the guest VM. On the details Select Processor, then
hit the "Copy host CPU configuration". Then you can start up the guest VM.
So for a RHEL6 guest on a F19 host:
$ perf stat ls
Performance counter stats for 'ls':
0.680177 task-clock # 0.728 CPUs utilized
0 context-switches # 0.000 K/sec
0 cpu-migrations # 0.000 K/sec
242 page-faults # 0.356 M/sec
1,138,470 cycles # 1.674 GHz
1,334,983 stalled-cycles-frontend # 117.26% frontend cycles idle
1,162,180 stalled-cycles-backend # 102.08% backend cycles idle
932,252 instructions # 0.82 insns per cycle
# 1.43 stalled cycles per insn
189,550 branches # 278.677 M/sec
10,156 branch-misses # 5.36% of all branches
[37.47%]
0.000933886 seconds time elapsed
However, the numbers do look a bit off for stalled-cycles-frontend and
stalled-cycles-backend.
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