If guest kernel is configured with nopvspin, or guest find its has
dedicated pCPUs from realtime hint feature, the pvspinlock will be
disabled, and vCPU preemption check is disabled too.
but KVM still can emulating HLT for vCPU for both cases, and check
if vCPU is preempted or not, and can boost performance
Like unixbench, single copy
Testcase Base with patch
System Benchmarks Index Values INDEX INDEX
Dhrystone 2 using register variables 3278.4 3277.7
Double-Precision Whetstone 822.8 825.8
Execl Throughput 1296.5 941.1
File Copy 1024 bufsize 2000 maxblocks 2124.2 2142.7
File Copy 256 bufsize 500 maxblocks 1335.9 1353.6
File Copy 4096 bufsize 8000 maxblocks 4256.3 4760.3
Pipe Throughput 1050.1 1054.0
Pipe-based Context Switching 243.3 352.0
Process Creation 820.1 814.4
Shell Scripts (1 concurrent) 2169.0 2086.0
Shell Scripts (8 concurrent) 7710.3 7576.3
System Call Overhead 672.4 673.9
======== =======
System Benchmarks Index Score 1467.2 1483.0
Co-developed-by: Wang GuangJu <wangguangju@xxxxxxxxx>
Signed-off-by: Wang GuangJu <wangguangju@xxxxxxxxx>
Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
---
arch/x86/kernel/kvm.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index a438217..7334649 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -1048,6 +1048,11 @@ void __init kvm_spinlock_init(void)
return;
}
+ if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
+ pv_ops.lock.vcpu_is_preempted =
+ PV_CALLEE_SAVE(__kvm_vcpu_is_preempted);
+ }
+
/*
* Disable PV spinlocks and use native qspinlock when dedicated pCPUs
* are available.
@@ -1076,10 +1081,6 @@ void __init kvm_spinlock_init(void)
pv_ops.lock.wait = kvm_wait;
pv_ops.lock.kick = kvm_kick_cpu;
- if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
- pv_ops.lock.vcpu_is_preempted =
- PV_CALLEE_SAVE(__kvm_vcpu_is_preempted);
- }
/*
* When PV spinlock is enabled which is preferred over
* virt_spin_lock(), virt_spin_lock_key's value is meaningless.
--
2.9.4
