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authorHeiko Carstens <heiko.carstens@de.ibm.com>2009-04-09 18:48:34 +0200
committerIngo Molnar <mingo@elte.hu>2009-04-09 19:28:24 +0200
commit36cd3c9f925b9307236505ae7ad1ad7ac4d4357c (patch)
treed9be68502d0f11b2259427e9ee8320891367143c /arch/s390/Kconfig
parent022624a758dc9489388a99ad29577b4c8c09237c (diff)
downloadlinux-linaro-android-36cd3c9f925b9307236505ae7ad1ad7ac4d4357c.tar.gz
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>
Diffstat (limited to 'arch/s390/Kconfig')
-rw-r--r--arch/s390/Kconfig1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index dcb667c4375..2eca5fe0e75 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -82,6 +82,7 @@ config S390
select USE_GENERIC_SMP_HELPERS if SMP
select HAVE_SYSCALL_WRAPPERS
select HAVE_FUNCTION_TRACER
+ select HAVE_DEFAULT_NO_SPIN_MUTEXES
select HAVE_OPROFILE
select HAVE_KPROBES
select HAVE_KRETPROBES