From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
Dapeng Mi <dapeng1.mi@intel.com>
Cc: rafael@kernel.org, daniel.lezcano@linaro.org,
linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, zhenyuw@linux.intel.com
Subject: Re: [PATCH] KVM: x86: use TPAUSE to replace PAUSE in halt polling
Date: Wed, 24 Aug 2022 19:19:08 +0200 [thread overview]
Message-ID: <f1598980-92a8-267c-cade-8f62d7653017@redhat.com> (raw)
In-Reply-To: <YwZDL4yv7F2Y4JBP@google.com>
On 8/24/22 17:26, Sean Christopherson wrote:
> I say "if", because I think this needs to come with performance numbers to show
> the impact on guest latency so that KVM and its users can make an informed decision.
> And if it's unlikely that anyone will ever want to enable TPAUSE for halt polling,
> then it's not worth the extra complexity in KVM.
Yeah, halt polling works around perhaps the biggest performance issue
with VMs compared to bare metal (so much that it's even possible to move
halt polling _inside_ the guest for extra performance).
I am ready to be proven wrong but I doubt TPAUSE will have a small
effect, and if one wants the most power saving they should disable halt
polling. Perhaps KVM could do it automatically if the powersaving
governor is in effect?
Paolo
next prev parent reply other threads:[~2022-08-24 17:19 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-24 9:11 [PATCH] KVM: x86: use TPAUSE to replace PAUSE in halt polling Dapeng Mi
2022-08-24 14:08 ` David Laight
2022-08-25 11:08 ` Mi, Dapeng1
2022-08-24 15:26 ` Sean Christopherson
2022-08-24 17:19 ` Paolo Bonzini [this message]
2022-08-25 12:16 ` Mi, Dapeng1
2022-08-25 11:31 ` Mi, Dapeng1
2022-08-26 10:14 ` Paolo Bonzini
2022-08-30 5:56 ` Mi, Dapeng1
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