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From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
Subject: Re: [RFC PATCH V2 4/4] Utilize the vmx preemption timer for tsc
 deadline timer
Date: Wed, 25 May 2016 15:38:57 +0200
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Cc: David Matlack <dmatlack@google.com>,
	Yunhong Jiang <yunhong.jiang@linux.intel.com>,
	kvm list <kvm@vger.kernel.org>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Wanpeng Li <kernellwp@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
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2016-05-25 12:40+0200, Paolo Bonzini:
> On 25/05/2016 01:11, David Matlack wrote:
>> > However, it possibly has impact if the vCPU thread is scheduled in/out
>> > very frequently, because it switches from/to the hrtimer emulation a lot.
>> 
>> What is the cost of the extra sched-in/out hooks?
> 
> I still have to review this version of the patches, but I think they can
> be removed and moved to blocking/unblocking instead.

I this so as well.  hrtimer does not make a difference to a preempted
VCPU or VCPU in userspace, only the blocking sleep needs to be
interrupted.