Messages in this thread |  | | | Subject | Re: [Bugme-new] [Bug 12562] New: High overhead while switching or synchronizing threads on different cores | | From | Mike Galbraith <> | | Date | Fri, 30 Jan 2009 08:57:50 +0100 |
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On Thu, 2009-01-29 at 15:05 +0100, Thomas Pilarski wrote: > > In short this program is carefully crafted to defeat all our affinity > > tests - and I'm not sure what to do. > > I am sorry, although it is not carefully crafted. The function random() > is causing my problem. I currently have no real data, so I tried to make > some random utilization and data.
Yeah, rather big difference, mega-contention vs zero-contention.
2.6.28.2, profile of ThreadSchedulingIssue 4 524288 8 200
vma samples % app name symbol name ffffffff80251efa 2574819 31.6774 vmlinux futex_wake ffffffff80251a39 1367613 16.8255 vmlinux futex_wait 0000000000411790 815426 10.0320 ThreadSchedulingIssue random ffffffff8022b3b5 343692 4.2284 vmlinux task_rq_lock 0000000000404e30 299316 3.6824 ThreadSchedulingIssue __lll_lock_wait_private ffffffff8030d430 262906 3.2345 vmlinux copy_user_generic_string ffffffff80462af2 235176 2.8933 vmlinux schedule 0000000000411b90 210984 2.5957 ThreadSchedulingIssue random_r ffffffff80251730 129376 1.5917 vmlinux hash_futex ffffffff8020be10 123548 1.5200 vmlinux system_call ffffffff8020a679 119398 1.4689 vmlinux __switch_to ffffffff8022f49b 110068 1.3541 vmlinux try_to_wake_up ffffffff8024c4d1 106352 1.3084 vmlinux sched_clock_cpu ffffffff8020be20 102709 1.2636 vmlinux system_call_after_swapgs ffffffff80229a2d 100614 1.2378 vmlinux update_curr ffffffff80248309 86475 1.0639 vmlinux add_wait_queue ffffffff80253149 85969 1.0577 vmlinux do_futex Versus using myrand() free sample cruft generator from rand(3) manpage. Poof.
vma samples % app name symbol name 004002f4 979506 90.7113 ThreadSchedulingIssue myrand 00400b00 53348 4.9405 ThreadSchedulingIssue thread_consumer 00400c25 42710 3.9553 ThreadSchedulingIssue thread_producer
One of those "don't _ever_ do that" things?
-Mike
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