linux-kernel - Re: [PATCH v3 2/6] KVM: X86: Implement PV IPIs in linux guest

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Message-ID: <CANRm+Cwic4kV6sWUvDMVb7PRn0kjCW7xLMyN-G7Px+ciDZb9qQ@mail.gmail.com>
Date:   Fri, 20 Jul 2018 18:17:40 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Radim Krcmar <rkrcmar@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH v3 2/6] KVM: X86: Implement PV IPIs in linux guest

On Fri, 20 Jul 2018 at 17:51, Radim Krcmar <rkrcmar@...hat.com> wrote:
>
> 2018-07-20 11:33+0800, Wanpeng Li:
> > On Fri, 20 Jul 2018 at 00:28, Radim Krčmář <rkrcmar@...hat.com> wrote:
> > > 2018-07-03 14:21+0800, Wanpeng Li:
> > > But because it is very similar to x2apic, I'd really need some real
> > > performance data to see if this benefits a real workload.
> >
> > Thanks for your review, Radim! :) I will find another real benchmark
> > instead of the micro one to evaluate the performance.
>
> Analyzing the cpu bitmap for every IPI request on a non-small guest (at
> least 32 VCPUs, ideally >256) during various workloads could also
> provide some insight regardless of workload/benchmark result -- we want
> to know how many VM exits we would save.

I will try ebizzy benchmark, just complete the patchset w/ __uint128
which Paolo just suggested. In addition, I remember aliyun posted the
performance number for their online real workload "message oriented
middleware" from 800 k/s vmexits w/ PV IPIs to 150 k/s vmexits w/ PV
IPIs.

Regards,
Wanpeng Li