linux-kernel - Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33

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Message-ID: <20091222072213.GY4490@redhat.com>
Date:	Tue, 22 Dec 2009 09:22:13 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Gregory Haskins <gregory.haskins@...il.com>
Cc:	Anthony Liguori <anthony@...emonkey.ws>,
	Avi Kivity <avi@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	kvm@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org,
	"alacrityvm-devel@...ts.sourceforge.net" 
	<alacrityvm-devel@...ts.sourceforge.net>
Subject: Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33

On Mon, Dec 21, 2009 at 12:44:17PM -0500, Gregory Haskins wrote:
> >  They should be relatively rare
> > because obtaining good receive batching is pretty easy.
> 
> Batching is poor mans throughput (its easy when you dont care about
> latency), so we generally avoid as much as possible.
> 
> > Considering
> > these are lightweight exits (on the order of 1-2us),
> 
> APIC EOIs on x86 are MMIO based, so they are generally much heavier than
> that.  I measure at least 4-5us just for the MMIO exit on my Woodcrest,
> never mind executing the locking/apic-emulation code.
> 
With x2apic EOIs are not MMIO any longer.

--
			Gleb.
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