From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33
Date: Tue, 22 Dec 2009 09:22:13 +0200
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Cc: Anthony Liguori <anthony@codemonkey.ws>,
	Avi Kivity <avi@redhat.com>, Ingo Molnar <mingo@elte.hu>,
	kvm@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
	torvalds@linux-foundation.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	netdev@vger.kernel.org,
	"alacrityvm-devel@lists.sourceforge.net"
	<alacrityvm-devel@lists.sourceforge.net>
To: Gregory Haskins <gregory.haskins@gmail.com>
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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.