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SubjectRe: [PATCH] KVM: Boosting vCPUs that are delivering interrupts
Cc arm and powerpc people,
On Mon, 15 Jul 2019 at 18:53, Christian Borntraeger
<borntraeger@de.ibm.com> wrote:
>
>
>
> On 12.07.19 09:10, Wanpeng Li wrote:
> > From: Wanpeng Li <wanpengli@tencent.com>
> >
> > Inspired by commit 9cac38dd5d (KVM/s390: Set preempted flag during vcpu wakeup
> > and interrupt delivery), except the lock holder, we want to also boost vCPUs
> > that are delivering interrupts. Actually most smp_call_function_many calls are
> > synchronous ipi calls, the ipi target vCPUs are also good yield candidates.
> > This patch sets preempted flag during wakeup and interrupt delivery time.
> >
> > Testing on 80 HT 2 socket Xeon Skylake server, with 80 vCPUs VM 80GB RAM:
> > ebizzy -M
> >
> > vanilla boosting improved
> > 1VM 23000 21232 -9%
> > 2VM 2800 8000 180%
> > 3VM 1800 3100 72%
> >
> > Testing on my Haswell desktop 8 HT, with 8 vCPUs VM 8GB RAM, two VMs,
> > one running ebizzy -M, the other running 'stress --cpu 2':
> >
> > w/ boosting + w/o pv sched yield(vanilla)
> >
> > vanilla boosting improved
> > 1570 4000 55%
> >
> > w/ boosting + w/ pv sched yield(vanilla)
> >
> > vanilla boosting improved
> > 1844 5157 79%
> >
> > w/o boosting, perf top in VM:
> >
> > 72.33% [kernel] [k] smp_call_function_many
> > 4.22% [kernel] [k] call_function_i
> > 3.71% [kernel] [k] async_page_fault
> >
> > w/ boosting, perf top in VM:
> >
> > 38.43% [kernel] [k] smp_call_function_many
> > 6.31% [kernel] [k] async_page_fault
> > 6.13% libc-2.23.so [.] __memcpy_avx_unaligned
> > 4.88% [kernel] [k] call_function_interrupt
> This certainly made sense for s390 so I guess that this also makes sense
> for others.
> Nnote we (s390) do not use kvm_vcpu_kick, so this should not cause
> any issue for s390.
>
>
> >
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Radim Krčmář <rkrcmar@redhat.com>
> > Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> > ---
> > virt/kvm/kvm_main.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index b4ab59d..2c46705 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -2404,8 +2404,10 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
> > int me;
> > int cpu = vcpu->cpu;
> >
> > - if (kvm_vcpu_wake_up(vcpu))
> > + if (kvm_vcpu_wake_up(vcpu)) {
> > + vcpu->preempted = true;
> > return;
> > + }
> >
> > me = get_cpu();
> > if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))
> >
>

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