From: Waiman Long <longman@redhat.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, "Joe Mario" <jmario@redhat.com>
Subject: Re: [PATCH] x86/kvm: Don't use pvqspinlock code if only 1 vCPU
Date: Thu, 19 Jul 2018 09:34:58 -0400 [thread overview]
Message-ID: <24e1962a-075c-8168-5d95-033b826ee919@redhat.com> (raw)
In-Reply-To: <20180719011546.GB28585@char.US.ORACLE.com>
On 07/18/2018 09:15 PM, Konrad Rzeszutek Wilk wrote:
> On Tue, Jul 17, 2018 at 05:59:27PM -0400, Waiman Long wrote:
>> On a VM with only 1 vCPU, the locking fast path will always be
>> successful. In this case, there is no need to use the the PV qspinlock
>> code which has higher overhead on the unlock side than the native
>> qspinlock code.
> Why not make this global? That is for both KVM and Xen and any
> other virtualized guest that uses this?
Right, I will send another patch for Xen. The pvqspinlock code has to be
explicitly opted in. Right now, both Xen and KVM used it in the tree. I
am not sure about other out-of-tree modules. There is nothing I can do
for those.
Cheers,
Longman
prev parent reply other threads:[~2018-07-19 13:35 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-17 21:59 [PATCH] x86/kvm: Don't use pvqspinlock code if only 1 vCPU Waiman Long
2018-07-18 11:51 ` Paolo Bonzini
2018-07-19 1:15 ` Konrad Rzeszutek Wilk
2018-07-19 13:34 ` Waiman Long [this message]
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