Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-12-27 13:22:23 +00:00
Code Issues Packages Projects Releases Wiki Activity

KVM: use cpu_relax when halt polling

Browse Source 
SMT siblings share caches and other hardware, and busy halt polling
will degrade its sibling performance if its sibling is working

Sean Christopherson suggested as below:

"Rather than disallowing halt-polling entirely, on x86 it should be
sufficient to simply have the hardware thread yield to its sibling(s)
via PAUSE.  It probably won't get back all performance, but I would
expect it to be close.
This compiles on all KVM architectures, and AFAICT the intended usage
of cpu_relax() is identical for all architectures."

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Message-Id: <20210727111247.55510-1-lirongqing@baidu.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Li RongQing 2021-07-27 19:12:47 +08:00 committed by Paolo Bonzini
parent 5868b8225e
commit 7477565433
1 changed files with 1 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
virt/kvm/kvm_main.c
View File

@ -3110,6 +3110,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
++vcpu->stat.generic.halt_poll_invalid; ++vcpu->stat.generic.halt_poll_invalid;
goto out; goto out;
} }
cpu_relax();
poll_end = cur = ktime_get(); poll_end = cur = ktime_get();
} while (kvm_vcpu_can_poll(cur, stop)); } while (kvm_vcpu_can_poll(cur, stop));
} }