From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759082Ab2BONrY (ORCPT ); Wed, 15 Feb 2012 08:47:24 -0500 Received: from mx1.redhat.com ([209.132.183.28]:4119 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757491Ab2BONrW (ORCPT ); Wed, 15 Feb 2012 08:47:22 -0500 Message-ID: <4F3BB763.9080006@redhat.com> Date: Wed, 15 Feb 2012 15:47:15 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20111222 Thunderbird/9.0 MIME-Version: 1.0 To: Anthony Liguori CC: Rob Earhart , linux-kernel , KVM list , qemu-devel Subject: Re: [Qemu-devel] [RFC] Next gen kvm api References: <4F2AB552.2070909@redhat.com> <4F2E80A7.5040908@redhat.com> <4F3025FB.1070802@codemonkey.ws> <4F31132F.3010100@redhat.com> <4F31408F.80901@codemonkey.ws> <4F314B2A.4000709@redhat.com> <4F314F2C.4040100@codemonkey.ws> In-Reply-To: <4F314F2C.4040100@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/07/2012 06:19 PM, Anthony Liguori wrote: >> Ah. But then ioeventfd has that as well, unless the other end is in >> the kernel too. > > > Yes, that was my point exactly :-) > > ioeventfd/mmio-over-socketpair to adifferent thread is not faster than > a synchronous KVM_RUN + writing to an eventfd in userspace modulo a > couple of cheap syscalls. > > The exception is when the other end is in the kernel and there is > magic optimizations (like there is today with ioeventfd). vhost seems to schedule a workqueue item unconditionally. irqfd does have magic optimizations to avoid an extra schedule. -- error compiling committee.c: too many arguments to function