From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754030AbZENRpn (ORCPT ); Thu, 14 May 2009 13:45:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752590AbZENRpd (ORCPT ); Thu, 14 May 2009 13:45:33 -0400 Received: from gw.goop.org ([64.81.55.164]:49101 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752270AbZENRpc (ORCPT ); Thu, 14 May 2009 13:45:32 -0400 Message-ID: <4A0C58BB.3090303@goop.org> Date: Thu, 14 May 2009 10:45:31 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Jan Beulich CC: Ingo Molnar , Jun Nakajima , Xiaohui Xin , Xin Li , Xen-devel , Nick Piggin , Linux Kernel Mailing List , "H. Peter Anvin" Subject: Re: [Xen-devel] Performance overhead of paravirt_ops on nativeidentified References: <4A0B62F7.5030802@goop.org> <4A0BED040200007800000DB0@vpn.id2.novell.com> In-Reply-To: <4A0BED040200007800000DB0@vpn.id2.novell.com> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jan Beulich wrote: > Wouldn't a third solution be to use ticket spinlocks everywhere, i.e. eliminate > the current indirection, and replace it by an indirection for just the contention > case? As I view it, the problem for Xen aren't really the ticket locks by > themselves, but rather the extra spinning involved, which is of concern only > if a lock is contended. We're using ticket locks quite happily in our kernels, > with directed instead of global wakeup from the unlock path. Do you have a patch to illustrate what you mean? How do you keep track of the target vcpu for the directed wakeup? Are you using the event-poll mechanism to block? J