KVM: LAPIC: Recalculate apic map in batch

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In the vCPU reset and set APIC_BASE MSR path, the apic map will be recalculated
several times, each time it will consume 10+ us observed by ftrace in my
non-overcommit environment since the expensive memory allocate/mutex/rcu etc
operations. This patch optimizes it by recaluating apic map in batch, I hope
this can benefit the serverless scenario which can frequently create/destroy
VMs.

Before patch:

kvm_lapic_reset  ~27us

After patch:

kvm_lapic_reset  ~14us

Observed by ftrace, improve ~48%.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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This commit is contained in:

Wanpeng Li 2020-02-26 10:41:02 +08:00 • committed by Paolo Bonzini

parent 49f933d445

commit 4abaffce4d

4 changed files with 39 additions and 10 deletions

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1

arch/x86/include/asm/kvm_host.h

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46

arch/x86/kvm/lapic.c

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arch/x86/kvm/lapic.h

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arch/x86/kvm/x86.c

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