From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC] Next gen kvm api Date: Tue, 07 Feb 2012 14:03:59 +0200 Message-ID: <4F31132F.3010100@redhat.com> References: <4F2AB552.2070909@redhat.com> <4F2E80A7.5040908@redhat.com> <4F3025FB.1070802@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Rob Earhart , linux-kernel , KVM list , qemu-devel To: Anthony Liguori Return-path: In-Reply-To: <4F3025FB.1070802@codemonkey.ws> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org List-Id: kvm.vger.kernel.org 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.