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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 <xinhui.pan@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Cc: David.Laight@ACULAB.COM Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: benh@kernel.crashing.org Cc: boqun.feng@gmail.com Cc: borntraeger@de.ibm.com Cc: bsingharora@gmail.com Cc: dave@stgolabs.net Cc: jgross@suse.com Cc: kernellwp@gmail.com Cc: konrad.wilk@oracle.com Cc: linuxppc-dev@lists.ozlabs.org Cc: mpe@ellerman.id.au Cc: paulmck@linux.vnet.ibm.com Cc: paulus@samba.org Cc: rkrcmar@redhat.com Cc: virtualization@lists.linux-foundation.org Cc: will.deacon@arm.com Cc: xen-devel-request@lists.xenproject.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1478077718-37424-10-git-send-email-xinhui.pan@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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1 changed files with 12 additions and 0 deletions
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@ -415,6 +415,15 @@ void kvm_disable_steal_time(void)
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wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
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}
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static bool kvm_vcpu_is_preempted(int cpu)
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{
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struct kvm_steal_time *src;
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src = &per_cpu(steal_time, cpu);
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return !!src->preempted;
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}
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#ifdef CONFIG_SMP
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static void __init kvm_smp_prepare_boot_cpu(void)
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{
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@ -471,6 +480,9 @@ void __init kvm_guest_init(void)
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if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
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has_steal_clock = 1;
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pv_time_ops.steal_clock = kvm_steal_clock;
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#ifdef CONFIG_PARAVIRT_SPINLOCKS
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pv_lock_ops.vcpu_is_preempted = kvm_vcpu_is_preempted;
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#endif
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}
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if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
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