From: Christophe de Dinechin <christophe.de.dinechin@gmail.com>
To: Dario Faggioli <dfaggioli@suse.com>
Cc: "Wanpeng Li" <kernellwp@gmail.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Thomas Gleixner" <tglx@linutronix.de>
Subject: Re: [PATCH] KVM: Disable wake-affine vCPU process to mitigate lock holder preemption
Date: Fri, 02 Aug 2019 10:30:11 +0200 [thread overview]
Message-ID: <7h7e7wkm0c.fsf@crazypad.dinechin.lan> (raw)
In-Reply-To: <04700afaf68114b5ab329f5a5182e21578c15795.camel@suse.com>
Dario Faggioli writes:
> On Tue, 2019-07-30 at 17:33 +0800, Wanpeng Li wrote:
>> However, in multiple VMs over-subscribe virtualization scenario, it
>> increases
>> the probability to incur vCPU stacking which means that the sibling
>> vCPUs from
>> the same VM will be stacked on one pCPU. I test three 80 vCPUs VMs
>> running on
>> one 80 pCPUs Skylake server(PLE is supported), the ebizzy score can
>> increase 17%
>> after disabling wake-affine for vCPU process.
>>
> Can't we achieve this by removing SD_WAKE_AFFINE from the relevant
> scheduling domains? By acting on
> /proc/sys/kernel/sched_domain/cpuX/domainY/flags, I mean?
>
> Of course this will impact all tasks, not only KVM vcpus. But if the
> host does KVM only anyway...
Even a host dedicated to KVM has many non-KVM processes. I suspect an
increasing number of hosts will be split between VMs and containers.
>
> Regards
--
Cheers,
Christophe de Dinechin
next prev parent reply other threads:[~2019-08-02 8:30 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 9:33 Wanpeng Li
2019-07-30 11:46 ` Paolo Bonzini
2019-08-01 12:39 ` Dario Faggioli
2019-07-30 12:09 ` Peter Zijlstra
2019-08-01 12:57 ` Dario Faggioli
2019-08-02 0:51 ` Wanpeng Li
2019-08-02 8:30 ` Christophe de Dinechin [this message]
2019-08-02 8:38 ` Paolo Bonzini
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