From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754166Ab0IPKNg (ORCPT ); Thu, 16 Sep 2010 06:13:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45208 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753672Ab0IPKNe (ORCPT ); Thu, 16 Sep 2010 06:13:34 -0400 Date: Thu, 16 Sep 2010 12:13:32 +0200 From: Gleb Natapov To: "Michael S. Tsirkin" Cc: Avi Kivity , Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] kvm: enable irq injection from interrupt context Message-ID: <20100916101332.GW3008@redhat.com> References: <20100915185417.GA3924@redhat.com> <20100916090256.GU3008@redhat.com> <20100916091054.GA20864@redhat.com> <20100916092553.GV3008@redhat.com> <4C91E75B.6010704@redhat.com> <20100916095310.GG20864@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100916095310.GG20864@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 16, 2010 at 11:53:10AM +0200, Michael S. Tsirkin wrote: > On Thu, Sep 16, 2010 at 11:46:03AM +0200, Avi Kivity wrote: > > On 09/16/2010 11:25 AM, Gleb Natapov wrote: > > >> > > >> MSI only appeared in rhel6, older guests still use level interrupts. > > >So they are already slow for other reasons. > > > > > > > Exactly, for example they need to exit to userspace to ack the > > interrupt. That's far slower than the workqueue. > > Well, this is not exactly comparable: you might get > same irq asserted multiple times and only deasserted once. > Are we talking about level interrupts? Why would you assert level triggered interrupt multiple times before deasserting it? -- Gleb.