Commit-ID: 1885aa7041c9e801e5d5b093b9dad38937ca37f6
Gitweb: http://git.kernel.org/tip/1885aa7041c9e801e5d5b093b9dad38937ca37f6
Author: Pan Xinhui <[email protected]>
AuthorDate: Wed, 2 Nov 2016 05:08:36 -0400
Committer: Ingo Molnar <[email protected]>
CommitDate: Tue, 22 Nov 2016 12:48:08 +0100
x86/kvm: Support the vCPU preemption check
Support the vcpu_is_preempted() functionality under KVM. This will
enhance lock performance on overcommitted hosts (more runnable vCPUs
than physical CPUs in the system) as doing busy waits for preempted
vCPUs will hurt system performance far worse than early yielding.
struct kvm_steal_time::preempted indicates that if one vCPU is running or
not after commit "x86, kvm/x86.c: support vCPU preempted check".
unix benchmark result:
host: kernel 4.8.1, i5-4570, 4 cpus
guest: kernel 4.8.1, 8 vcpus
test-case after-patch before-patch
Execl Throughput | 18307.9 lps | 11701.6 lps
File Copy 1024 bufsize 2000 maxblocks | 1352407.3 KBps | 790418.9 KBps
File Copy 256 bufsize 500 maxblocks | 367555.6 KBps | 222867.7 KBps
File Copy 4096 bufsize 8000 maxblocks | 3675649.7 KBps | 1780614.4 KBps
Pipe Throughput | 11872208.7 lps | 11855628.9 lps
Pipe-based Context Switching | 1495126.5 lps | 1490533.9 lps
Process Creation | 29881.2 lps | 28572.8 lps
Shell Scripts (1 concurrent) | 23224.3 lpm | 22607.4 lpm
Shell Scripts (8 concurrent) | 3531.4 lpm | 3211.9 lpm
System Call Overhead | 10385653.0 lps | 10419979.0 lps
Signed-off-by: Pan Xinhui <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Paolo Bonzini <[email protected]>
Cc: [email protected]
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/kernel/kvm.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index edbbfc8..0b48dd2 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -415,6 +415,15 @@ void kvm_disable_steal_time(void)
wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
}
+static bool kvm_vcpu_is_preempted(int cpu)
+{
+ struct kvm_steal_time *src;
+
+ src = &per_cpu(steal_time, cpu);
+
+ return !!src->preempted;
+}
+
#ifdef CONFIG_SMP
static void __init kvm_smp_prepare_boot_cpu(void)
{
@@ -471,6 +480,9 @@ void __init kvm_guest_init(void)
if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
has_steal_clock = 1;
pv_time_ops.steal_clock = kvm_steal_clock;
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+ pv_lock_ops.vcpu_is_preempted = kvm_vcpu_is_preempted;
+#endif
}
if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
