Messages in this thread | | | Date | Tue, 14 Feb 2006 09:09:42 +0100 | From | Heiko Carstens <> | Subject | Re: calibrate_migration_costs takes ages on s390 |
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> > We did a bit of testing, -rc2-git3 + the patch below was still ok. > > > > [PATCH] s390: earlier initialization of cpu_possible_map > > 9733e2407ad2237867cb13c04e7d619397fa3090 > > I need to double check, but -git5 + that patch was reported to be slow.
I did a quick git bisect search. This is one is the hurting one:
Author: Ingo Molnar <mingo@elte.hu> 2006-02-07 21:58:54 Committer: Linus Torvalds <torvalds@g5.osdl.org> 2006-02-08 01:12:33 Parent: 8519fb30e438f8088b71a94a7d5a660a814d3872 ([PATCH] mm: compound release fix) Child: 0d4c3e7a8c65892c7d6a748fdbb4499e988880db ([PATCH] unshare system call -v5: Documentation file)
[PATCH] Fix spinlock debugging delays to not time out too early The spinlock-debug wait-loop was using loops_per_jiffy to detect too long spinlock waits - but on fast CPUs this led to a way too fast timeout and false messages. The fix is to include a __delay(1) call in the loop, to correctly approximate the intended delay timeout of 1 second. The code assumes that every architecture implements __delay(1) to last around 1/(loops_per_jiffy*HZ) seconds. Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I guess we're once again suffering from being a virtualized platform: the formerly used call to cpu_relax() informed the underlying hypervisor that we want to give up the current cpu while __delay() keeps it. Unless we're scheduled away involuntarily. The "Detect Soft Lockups" option doesn't make too much sense too on our platform, since we get a lot of false positives. Quick fix: turn off the options CONFIG_DEBUG_SPINLOCK and CONFIG_DETECT_SOFTLOCKUP.
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