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authorChristian Borntraeger <borntraeger@de.ibm.com>2016-05-13 12:16:36 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2016-05-13 17:29:49 +0200
commitc4a8de357ef1916c38e4419c0bafad86ca4fbcf7 (patch)
treebf00e3c8077771a5dcfd641ea5ed4643ae645618 /arch
parent3491caf2755e9f312666712510d80b00c81ff247 (diff)
KVM: s390: set halt polling to 80 microseconds
on s390 we disabled the halt polling with commit 920552b213e3 ("KVM: disable halt_poll_ns as default for s390x"), as floating interrupts would let all CPUs have a successful poll, resulting in much higher CPU usage (on otherwise idle systems). With the improved selection of polls we can now retry halt polling. Performance measurements with different choices like 25,50,80,100,200 microseconds showed that 80 microseconds seems to improve several cases without increasing the CPU costs too much. Higher values would improve the performance even more but increased the cpu time as well. So let's start small and use this value of 80 microseconds on s390 until we have a better understanding of cost/benefit of higher values. Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/s390/include/asm/kvm_host.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 53d794538067..37b9017c6a96 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -38,7 +38,7 @@
*/
#define KVM_NR_IRQCHIPS 1
#define KVM_IRQCHIP_NUM_PINS 4096
-#define KVM_HALT_POLL_NS_DEFAULT 0
+#define KVM_HALT_POLL_NS_DEFAULT 80000
/* s390-specific vcpu->requests bit members */
#define KVM_REQ_ENABLE_IBS 8