linux-kernel - Re: [PATCH v4 0/3] KVM: Introduce dedicated vCPUs hint KVM_HINTS

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Message-ID: <20180306143939.GA23766@u40b0340c692b58f6553c.ant.amazon.com>
Date:   Tue, 6 Mar 2018 06:39:39 -0800
From:   Eduardo Valentin <eduval@...zon.com>
To:     Wanpeng Li <kernellwp@...il.com>
CC:     <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Eduardo Habkost <ehabkost@...hat.com>
Subject: Re: [PATCH v4 0/3] KVM: Introduce dedicated vCPUs hint
 KVM_HINTS_DEDICATED

Folks,

On Tue, Feb 13, 2018 at 09:05:39AM +0800, Wanpeng Li wrote:
> This patchset introduces dedicated vCPUs(vCPU pinning, and there is no 
> vCPU over-commitment) hint KVM_HINTS_DEDICATED, it has two users now:
> 
> 1) Waiman Long mentioned that:
> 
>     Generally speaking, unfair lock performs well for VMs with a small
>     number of vCPUs. Native qspinlock may perform better than pvqspinlock
>     if there is vCPU pinning and there is no vCPU over-commitment.
> 
> 2) vCPUs are very unlikely to get preempted when they are the only task 
>    running on a CPU. PV TLB flush is slower that the native flush in that 
>    case.
> 
> v3 -> v4:
>  * update feature bit document
> v2 -> v3:
>  * a separate table for CPUID[0x40000001].EDX bits
>  * a new kvm_hint_has_feature macro
> v1 -> v2:
>  * update to KVM_HINTS_DEDICATED

Great to see this has finally moved forward! Thanks for picking it up Wanpeng.

I would just request to next time at least reference the original thread and
copy the original authors of the patch/idea.

Thanks a lot.

-- 
All the best,
Eduardo Valentin