> > 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 <[email protected]> 2006-02-07 21:58:54
Committer: Linus Torvalds <[email protected]> 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 <[email protected]>
Cc: Andi Kleen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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.
Heiko
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