* [Bug runtime/15912] New: on rawhide, we're getting perf probe read errors
@ 2013-08-30 15:08 dsmith at redhat dot com
2013-08-30 15:11 ` [Bug runtime/15912] " dsmith at redhat dot com
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: dsmith at redhat dot com @ 2013-08-30 15:08 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=15912
Bug ID: 15912
Summary: on rawhide, we're getting perf probe read errors
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: runtime
Assignee: systemtap at sourceware dot org
Reporter: dsmith at redhat dot com
On rawhide (3.11.0-0.rc6.git4.1.fc21.x86_64), although the perf.exp testcase
passes, the log file shows several errors, like 'ERROR: _stp_perf_read':
====
spawn /usr/local/bin/stap -c towers.x -e
global towers
global main
probe perf.hw.instructions.process("towers.x").counter("a")
{
counter_a += 1
}
probe perf.hw.instructions.process("towers.x").counter("b")
{
counter_b += 1
}
probe process("towers.x").statement("towers@towers.c")
{
towers <<< @perf("a")
}
probe process("towers.x").statement("main@towers.c")
{
main <<< @perf("b")
}
probe end
{
printf("count main=%d\ncount towers=%d\ncounter %d/%d\n",
@count(main), @count(towers), counter_a, counter_b)
printf("min main=%d\nmin towers=%d\n", @min(main),
@min(towers))
printf("max main=%d\nmax towers=%d\n", @max(main),
@max(towers))
}
WARNING: Statements in perf counter probe will never be reached.: operator '{'
at /usr/local/share/systemtap/tapset/linux/perf.stp:12:60^M
source: probe perf.hw.instructions = perf.type(0).config(1) { }
^
WARNING: never-assigned local variable 'counter_a' (alternatives: counter_b
towers main): identifier 'counter_a' at <input>:28:36
source: @count(main), @count(towers), counter_a, counter_b)
^
WARNING: never-assigned local variable 'counter_b' (alternatives: counter_a
towers main): identifier 'counter_b' at :28:47
source: @count(main), @count(towers), counter_a, counter_b)
^
WARNING: perf probe
'perf.type(0).config(1).sample(0).process("towers.x").counter("b")' is not
supported by this kernel (-2).
WARNING: perf probe
'perf.type(0).config(1).sample(0).process("towers.x").counter("a")' is not
supported by this kernel (-2).
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
count main=1
count towers=19
counter 0/0
min main=0
min towers=0
max main=0
max towers=0
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
ERROR: _stp_perf_read
WARNING: /usr/local/bin/staprun exited with status: 1
Pass 5: run failed. [man error::pass5]
====
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* [Bug runtime/15912] on rawhide, we're getting perf probe read errors
2013-08-30 15:08 [Bug runtime/15912] New: on rawhide, we're getting perf probe read errors dsmith at redhat dot com
@ 2013-08-30 15:11 ` dsmith at redhat dot com
2014-01-14 20:44 ` dsmith at redhat dot com
2014-01-15 15:50 ` wcohen at redhat dot com
2 siblings, 0 replies; 4+ messages in thread
From: dsmith at redhat dot com @ 2013-08-30 15:11 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=15912
--- Comment #1 from David Smith <dsmith at redhat dot com> ---
Created attachment 7177
--> https://sourceware.org/bugzilla/attachment.cgi?id=7177&action=edit
full systemtap.log
Here's the full systemtap.log from that test run.
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* [Bug runtime/15912] on rawhide, we're getting perf probe read errors
2013-08-30 15:08 [Bug runtime/15912] New: on rawhide, we're getting perf probe read errors dsmith at redhat dot com
2013-08-30 15:11 ` [Bug runtime/15912] " dsmith at redhat dot com
@ 2014-01-14 20:44 ` dsmith at redhat dot com
2014-01-15 15:50 ` wcohen at redhat dot com
2 siblings, 0 replies; 4+ messages in thread
From: dsmith at redhat dot com @ 2014-01-14 20:44 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=15912
David Smith <dsmith at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from David Smith <dsmith at redhat dot com> ---
From some further investigation, it looks like these errors are expected. Those
error messages are output since those hw perf counter probes don't work on this
virtual machine.
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* [Bug runtime/15912] on rawhide, we're getting perf probe read errors
2013-08-30 15:08 [Bug runtime/15912] New: on rawhide, we're getting perf probe read errors dsmith at redhat dot com
2013-08-30 15:11 ` [Bug runtime/15912] " dsmith at redhat dot com
2014-01-14 20:44 ` dsmith at redhat dot com
@ 2014-01-15 15:50 ` wcohen at redhat dot com
2 siblings, 0 replies; 4+ messages in thread
From: wcohen at redhat dot com @ 2014-01-15 15:50 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=15912
William Cohen <wcohen at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
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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2013-08-30 15:08 [Bug runtime/15912] New: on rawhide, we're getting perf probe read errors dsmith at redhat dot com
2013-08-30 15:11 ` [Bug runtime/15912] " dsmith at redhat dot com
2014-01-14 20:44 ` dsmith at redhat dot com
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