From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:39683) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RujmJ-0001Fz-6h for qemu-devel@nongnu.org; Tue, 07 Feb 2012 07:04:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RujmG-0005NV-Sg for qemu-devel@nongnu.org; Tue, 07 Feb 2012 07:04:07 -0500 Received: from mx1.redhat.com ([209.132.183.28]:18183) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RujmG-0005NL-JM for qemu-devel@nongnu.org; Tue, 07 Feb 2012 07:04:04 -0500 Message-ID: <4F31132F.3010100@redhat.com> Date: Tue, 07 Feb 2012 14:03:59 +0200 From: Avi Kivity MIME-Version: 1.0 References: <4F2AB552.2070909@redhat.com> <4F2E80A7.5040908@redhat.com> <4F3025FB.1070802@codemonkey.ws> In-Reply-To: <4F3025FB.1070802@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC] Next gen kvm api List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Rob Earhart , linux-kernel , KVM list , qemu-devel On 02/06/2012 09:11 PM, Anthony Liguori wrote: > > I'm not so sure. ioeventfds and a future mmio-over-socketpair have to > put the kthread to sleep while it waits for the other end to process > it. This is effectively equivalent to a heavy weight exit. The > difference in cost is dropping to userspace which is really neglible > these days (< 100 cycles). On what machine did you measure these wonderful numbers? But I agree a heavyweight exit is probably faster than a double context switch on a remote core. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.