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| author | Wanpeng Li <wanpeng.li@hotmail.com> | 2017-12-12 17:33:02 -0800 |
|---|---|---|
| committer | Radim Krčmář <rkrcmar@redhat.com> | 2018-01-16 16:34:13 +0100 |
| commit | 858a43aae23672d46fe802a41f4748f322965182 (patch) | |
| tree | 8c895d46933e0a99b5578e12dab93bea0c5af377 /arch/x86/include/uapi | |
| parent | fa55eedd6328d3072e82218a2346b8752253af2d (diff) | |
| download | linux-0-day-858a43aae23672d46fe802a41f4748f322965182.tar.gz linux-0-day-858a43aae23672d46fe802a41f4748f322965182.tar.xz | |
KVM: X86: use paravirtualized TLB Shootdown
Remote TLB flush does a busy wait which is fine in bare-metal
scenario. But with-in the guest, the vcpus might have been pre-empted or
blocked. In this scenario, the initator vcpu would end up busy-waiting
for a long amount of time; it also consumes CPU unnecessarily to wake
up the target of the shootdown.
This patch set adds support for KVM's new paravirtualized TLB flush;
remote TLB flush does not wait for vcpus that are sleeping, instead
KVM will flush the TLB as soon as the vCPU starts running again.
The improvement is clearly visible when the host is overcommitted; in this
case, the PV TLB flush (in addition to avoiding the wait on the main CPU)
prevents preempted vCPUs from stealing precious execution time from the
running ones.
Testing on a Xeon Gold 6142 2.6GHz 2 sockets, 32 cores, 64 threads,
so 64 pCPUs, and each VM is 64 vCPUs.
ebizzy -M
vanilla optimized boost
1VM 46799 48670 4%
2VM 23962 42691 78%
3VM 16152 37539 132%
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Diffstat (limited to 'arch/x86/include/uapi')
| -rw-r--r-- | arch/x86/include/uapi/asm/kvm_para.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h index 15685bd22faa4..7a2ade4aa2353 100644 --- a/arch/x86/include/uapi/asm/kvm_para.h +++ b/arch/x86/include/uapi/asm/kvm_para.h @@ -25,6 +25,7 @@ #define KVM_FEATURE_STEAL_TIME 5 #define KVM_FEATURE_PV_EOI 6 #define KVM_FEATURE_PV_UNHALT 7 +#define KVM_FEATURE_PV_TLB_FLUSH 9 /* The last 8 bits are used to indicate how to interpret the flags field * in pvclock structure. If no bits are set, all flags are ignored. @@ -52,6 +53,7 @@ struct kvm_steal_time { }; #define KVM_VCPU_PREEMPTED (1 << 0) +#define KVM_VCPU_FLUSH_TLB (1 << 1) #define KVM_CLOCK_PAIRING_WALLCLOCK 0 struct kvm_clock_pairing { |