https://bugzilla.novell.com/show_bug.cgi?id=850794
https://bugzilla.novell.com/show_bug.cgi?id=850794#c11
--- Comment #11 from Borislav Petkov 2013-11-20 11:33:28 UTC ---
Ok, I've made the diff line-by-line so that it is visible what happens.
We're almost 5 seconds slower on 13.1 and the frontend stalled cycles
have more than doubled.
I'll need to reproduce this with the upstream kernels 3.7 and 3.11
and check whether we're seeing slowdown there too or is it some oS
configuration issue.
Now, to the question whether this has impact on your benchmark: maybe
but I don't see how since we're spending the largest amount of time in
the openmp library.
You could try to build the upstream kernel 3.12 and check whether you
see slowdown there too. You could also run this workload and your
benchmark to check.
What else you can do is try to build openmp yourself, tailored to your
machine (does openmp even have that possibility?) and see whether the
slowdown is still here.
HTH.
<tt>
--- perf_opensuse_12_3.txt 2013-11-20 12:16:58.813514215 +0100
+++ perf_opensuse_13_1.txt 2013-11-20 12:17:08.649514594 +0100
@@ -1,15 +1,15 @@
-Performance counter stats for 'make -s -j64 bzImage' (10 runs):
+ Performance counter stats for 'make -s -j64 bzImage' (10 runs):
- 4973413.267368 task-clock # 31.964 CPUs utilized
( +- 0.75% ) [100.00%]
+ 5134296.537332 task-clock # 32.031 CPUs utilized
( +- 1.07% ) [100.00%]
- 2402124 context-switches # 0.483 K/sec
( +- 1.57% ) [100.00%]
+ 1790103 context-switches # 0.349 K/sec
( +- 0.56% ) [100.00%]
- 141608 cpu-migrations # 0.028 K/sec
( +- 3.47% ) [100.00%]
+ 159027 cpu-migrations # 0.031 K/sec
( +- 0.80% ) [100.00%]
- 38497110 page-faults # 0.008 M/sec
( +- 0.20% )
+ 40298747 page-faults # 0.008 M/sec
( +- 0.19% )
- 4142081359677 cycles # 0.833 GHz
( +- 0.22% ) [82.03%]
+ 4615090037688 cycles # 0.899 GHz
( +- 0.28% ) [53.43%]
- 1774060105247 stalled-cycles-frontend # 42.83% frontend cycles idle
( +- 1.02% ) [82.97%]
+ 4071113200175 stalled-cycles-frontend # 88.21% frontend cycles idle
( +- 1.40% ) [76.03%]
- 312483264794 stalled-cycles-backend # 7.54% backend cycles idle
( +- 1.72% ) [35.00%]
+ 414509633016 stalled-cycles-backend # 8.98% backend cycles idle
( +- 0.77% ) [70.54%]
- 2573836596870 instructions # 0.62 insns per cycle
+ 2699077944491 instructions # 0.58 insns per cycle
- # 0.69 stalled cycles per
insn ( +- 0.96% ) [50.09%]
+ # 1.51 stalled cycles per
insn ( +- 0.15% ) [82.35%]
- 571886892860 branches # 114.989 M/sec
( +- 0.39% ) [66.32%]
+ 594529147760 branches # 115.796 M/sec
( +- 0.07% ) [83.36%]
- 30257738350 branch-misses # 5.29% of all branches
( +- 0.35% ) [81.93%]
+ 32308723628 branch-misses # 5.43% of all branches
( +- 0.11% ) [68.31%]
- 155.593738109 seconds time elapsed
( +- 0.75% )
+ 160.293796620 seconds time elapsed
( +- 1.07% )
</tt>
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