linux/arch/s390
Heiko Carstens 36cd3c9f92 mutex: have non-spinning mutexes on s390 by default
Impact: performance regression fix for s390

The adaptive spinning mutexes will not always do what one would expect on
virtualized architectures like s390. Especially the cpu_relax() loop in
mutex_spin_on_owner might hurt if the mutex holding cpu has been scheduled
away by the hypervisor.

We would end up in a cpu_relax() loop when there is no chance that the
state of the mutex changes until the target cpu has been scheduled again by
the hypervisor.

For that reason we should change the default behaviour to no-spin on s390.

We do have an instruction which allows to yield the current cpu in favour of
a different target cpu. Also we have an instruction which allows us to figure
out if the target cpu is physically backed.

However we need to do some performance tests until we can come up with
a solution that will do the right thing on s390.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
LKML-Reference: <20090409184834.7a0df7b2@osiris.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-09 19:28:24 +02:00
..
appldata Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6 2008-12-28 12:49:40 -08:00
boot
crypto Merge branch 'for-linus' of git://git390.marist.edu/pub/scm/linux-2.6 2009-03-26 16:04:22 -07:00
hypfs [S390] fix hypfs build failure 2009-03-31 19:17:03 +02:00
include/asm Merge branch 'ipi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-04-03 17:33:30 -07:00
kernel Simplify copy_thread() 2009-04-02 19:04:51 -07:00
kvm Merge branch 'for-linus' of git://git390.marist.edu/pub/scm/linux-2.6 2009-03-26 16:04:22 -07:00
lib [S390] use compiler builtin versions of strlen/strcpy/strcat 2009-03-26 15:24:24 +01:00
math-emu [S390] remove -traditional 2008-04-30 13:38:44 +02:00
mm [S390] cpumask: use mm_cpumask() wrapper 2009-03-26 15:24:34 +01:00
oprofile Combine instrumentation menus in kernel/Kconfig.instrumentation 2007-10-19 11:53:54 -07:00
defconfig [S390] Update default configuration. 2009-02-11 10:37:40 +01:00
Kconfig mutex: have non-spinning mutexes on s390 by default 2009-04-09 19:28:24 +02:00
Kconfig.debug generic debug pagealloc: build fix 2009-04-02 19:04:48 -07:00
Makefile [S390] Add processor type march=z10 and a processor type safety check. 2008-12-25 13:39:12 +01:00