linux-kernel - Re: [PATCH 2/2] KVM: x86: optimize delivery of TSC deadline timer interrupt

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Message-ID: <20150210193018.GA32006@amt.cnet>
Date:	Tue, 10 Feb 2015 17:30:18 -0200
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org, riel@...hat.com,
	rkrcmar@...hat.com, dmatlack@...gle.com
Subject: Re: [PATCH 2/2] KVM: x86: optimize delivery of TSC deadline timer
 interrupt

On Sat, Feb 07, 2015 at 09:33:09PM +0100, Paolo Bonzini wrote:
> > Can remove another 300 cycles from do_div when programming LAPIC
> > tscdeadline timer.
> 
> Do you mean using something like lib/reciprocal_div.c?  

Yes.

> Good idea,
> though that's not latency, it's just being slow. :)

It adds to latency, yes (the guest will reprogram the
APIC timer before resuming userspace execution).

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