答复: 答复: [PATCH] KVM: Consider SMT idle status when halt polling

From: "Li,Rongqing" <lirongqing@baidu.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Wanpeng Li <kernellwp@gmail.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>, kvm <kvm@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: 答复: 答复: [PATCH] KVM: Consider SMT idle status when halt polling
Date: Tue, 27 Jul 2021 06:39:58 +0000	[thread overview]
Message-ID: <e68a267a328648c484132bafd022671c@baidu.com> (raw)
In-Reply-To: <YP9gkSk+CHdKLP/Q@google.com>


> -----邮件原件-----
> 发件人: Sean Christopherson <seanjc@google.com>
> 发送时间: 2021年7月27日 9:26
> 收件人: Li,Rongqing <lirongqing@baidu.com>
> 抄送: Wanpeng Li <kernellwp@gmail.com>; Paolo Bonzini
> <pbonzini@redhat.com>; Ingo Molnar <mingo@redhat.com>; Peter Zijlstra
> <peterz@infradead.org>; kvm <kvm@vger.kernel.org>; LKML
> <linux-kernel@vger.kernel.org>
> 主题: Re: 答复: [PATCH] KVM: Consider SMT idle status when halt polling
> 
> 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.
> 

Reasonable, thanks, I will resend it

-Li


> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index
> 6980dabe9df5..a07ecb3c67fb 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3111,6 +3111,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
>                                 goto out;
>                         }
>                         poll_end = cur = ktime_get();
> +                       cpu_relax();
>                 } while (kvm_vcpu_can_poll(cur, stop));
>         }
>