linux-kernel - Re: [PATCH] KVM: x86: Run PIT work in own kthread

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Message-ID: <4F8D5ABC.4030705@redhat.com>
Date:	Tue, 17 Apr 2012 14:57:48 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Jan Kiszka <jan.kiszka@...mens.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>, kvm <kvm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86: Run PIT work in own kthread

On 04/17/2012 02:18 PM, Jan Kiszka wrote:
> On 2012-04-17 12:27, Avi Kivity wrote:
> > On 04/16/2012 09:26 PM, Jan Kiszka wrote:
> >> We can't run PIT IRQ injection work in the interrupt context of the host
> >> timer. This would allow the user to influence the handler complexity by
> >> asking for a broadcast to a large number of VCPUs. Therefore, this work
> >> was pushed into workqueue context in 9d244caf2e. However, this prevents
> >> prioritizing the PIT injection over other task as workqueues share
> >> kernel threads.
> >>
> >> This replaces the workqueue with a kthread worker and gives that thread
> >> a name in the format "kvm-pit/<owner-process-pid>". That allows to
> >> identify and adjust the kthread priority according to the VM process
> >> parameters.
> > 
> > Is this a new ABI?
>
> Yep. Scripts will use it, maybe even QEMU. Do you want this to appear in
> api.txt?

You already know the answer.

Please make it explicit that the thread is optional.  This way, if we
gain real-time workqueue support, or eliminate it through some other
trick, userspace won't break.

-- 
error compiling committee.c: too many arguments to function

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