linux-kernel - Re: [PATCH v2 2/3] KVM: X86: Implement PV sched yield hypercall

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Message-ID: <CANRm+Cx+Uhy+C4KUCkyhxQ9UPOak4Kwo0JNyxEtZ4vHQHRWmPQ@mail.gmail.com>
Date:   Tue, 28 May 2019 17:57:46 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Christian Borntraeger <borntraeger@...ibm.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH v2 2/3] KVM: X86: Implement PV sched yield hypercall

On Tue, 28 May 2019 at 17:12, Christian Borntraeger
<borntraeger@...ibm.com> wrote:
>
> On 28.05.19 02:53, Wanpeng Li wrote:
> > From: Wanpeng Li <wanpengli@...cent.com>
> >
> > The target vCPUs are in runnable state after vcpu_kick and suitable
> > as a yield target. This patch implements the sched yield hypercall.
> >
> > 17% performace increase 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).
> >
> > Cc: Paolo Bonzini <pbonzini@...hat.com>
> > Cc: Radim Krčmář <rkrcmar@...hat.com>
> > Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
>
> FWIW, we do have a similar interface in s390.
>
> See arch/s390/kvm/diag.c  __diag_time_slice_end_directed for our implementation.

Good to know this. :)

Regards,
Wanpeng Li