linux-kernel - Re: [PATCH] sched: introduce configurable delay before entering idle

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Message-ID: <20190514135022.GD4392@amt.cnet>
Date:   Tue, 14 May 2019 10:50:23 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     kvm-devel <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Bandan Das <bsd@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH] sched: introduce configurable delay before entering idle

On Mon, May 13, 2019 at 05:20:37PM +0800, Wanpeng Li wrote:
> On Wed, 8 May 2019 at 02:57, Marcelo Tosatti <mtosatti@...hat.com> wrote:
> >
> >
> > Certain workloads perform poorly on KVM compared to baremetal
> > due to baremetal's ability to perform mwait on NEED_RESCHED
> > bit of task flags (therefore skipping the IPI).
> 
> KVM supports expose mwait to the guest, if it can solve this?
> 
> Regards,
> Wanpeng Li

Unfortunately mwait in guest is not feasible (uncompatible with multiple
guests). Checking whether a paravirt solution is possible.