From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH 10/10] Introduce MSI message sending interface that bypass IRQ routing. Date: Sun, 9 Aug 2009 18:07:07 +0300 Message-ID: <20090809150707.GT4764@redhat.com> References: <1249821671-32356-1-git-send-email-gleb@redhat.com> <1249821671-32356-11-git-send-email-gleb@redhat.com> <4A7EE39E.40809@redhat.com> <20090809145245.GA4932@redhat.com> <4A7EE4BB.5070606@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from mx2.redhat.com ([66.187.237.31]:60657 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750827AbZHIPHI (ORCPT ); Sun, 9 Aug 2009 11:07:08 -0400 Received: from int-mx2.corp.redhat.com (int-mx2.corp.redhat.com [172.16.27.26]) by mx2.redhat.com (8.13.8/8.13.8) with ESMTP id n79F79E2001664 for ; Sun, 9 Aug 2009 11:07:09 -0400 Content-Disposition: inline In-Reply-To: <4A7EE4BB.5070606@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Sun, Aug 09, 2009 at 06:01:15PM +0300, Avi Kivity wrote: > On 08/09/2009 05:52 PM, Gleb Natapov wrote: >> On Sun, Aug 09, 2009 at 05:56:30PM +0300, Avi Kivity wrote: >> >>> On 08/09/2009 03:41 PM, Gleb Natapov wrote: >>> >>>> Sending of MSI using IRQ routing is an artificial concept and potentially >>>> big number of MSIs (2048 per device) make it also inefficient. This >>>> patch adds an interface to inject MSI messages from userspace to lapic >>>> logic directly. The patch also reduces the maximum number of IRQ routing >>>> entries to 128 since MSIs will no longer go there and 128 entries cover >>>> 5 ioapics and this ought to be enough for anybody. >>>> >>> In the future many MSIs will be triggered via irqfds, and those >>> require irq routing. >>> >>> >> Why? My plan is to change irqfd to use the MSI functions. >> >> > > It's still an "install handle, call handle" interface. Maybe it would > have been better to start off with your new interface, but having both > is too much for too little gain. > Is it not too late to change interface? There was no released kernel with irqfd yet. And this just adds another level of indirection and one more point of false cache sharing. -- Gleb.