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From: "Radim Krčmář" <rkrcmar@redhat.com>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH v3 0/3] KVM: Yield to IPI target if necessary
Date: Mon, 10 Jun 2019 16:34:20 +0200	[thread overview]
Message-ID: <20190610143420.GA6594@flask> (raw)
In-Reply-To: <1559178307-6835-1-git-send-email-wanpengli@tencent.com>

2019-05-30 09:05+0800, Wanpeng Li:
> The idea is from Xen, when sending a call-function IPI-many to vCPUs, 
> yield if any of the IPI target vCPUs was preempted. 17% performance 
> increasement of ebizzy benchmark can be observed in an over-subscribe 
> environment. (w/ kvm-pv-tlb disabled, testing TLB flush call-function 
> IPI-many since call-function is not easy to be trigged by userspace 
> workload).

Have you checked if we could gain performance by having the yield as an
extension to our PV IPI call?

It would allow us to skip the VM entry/exit overhead on the caller.
(The benefit of that might be negligible and it also poses a
 complication when splitting the target mask into several PV IPI
 hypercalls.)

Thanks.

  parent reply	other threads:[~2019-06-10 14:34 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-30  1:05 [PATCH v3 0/3] KVM: Yield to IPI target if necessary Wanpeng Li
2019-05-30  1:05 ` [PATCH v3 1/3] KVM: X86: " Wanpeng Li
2019-05-30  1:05 ` [PATCH v3 2/3] KVM: X86: Implement PV sched yield hypercall Wanpeng Li
2019-06-10 14:17   ` Radim Krčmář
2019-06-11  8:47     ` Wanpeng Li
2019-05-30  1:05 ` [PATCH v3 3/3] KVM: X86: Expose PV_SCHED_YIELD CPUID feature bit to guest Wanpeng Li
2019-06-10  5:58 ` [PATCH v3 0/3] KVM: Yield to IPI target if necessary Wanpeng Li
2019-06-10 14:34 ` Radim Krčmář [this message]
2019-06-11  1:11   ` Sean Christopherson
2019-06-11  1:45     ` Wanpeng Li
2019-06-11  1:48       ` Nadav Amit
2019-06-11 10:02         ` Wanpeng Li
2019-06-11 16:57           ` Nadav Amit
2019-06-12  1:18             ` Wanpeng Li
2019-06-12  1:37               ` Nadav Amit
2019-06-28  9:12                 ` Wanpeng Li
2019-06-28  9:18                   ` Wanpeng Li
2019-06-11 10:26   ` Wanpeng Li

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