From patchwork Mon Jun 25 09:55:33 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Bader X-Patchwork-Id: 167022 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from chlorine.canonical.com (chlorine.canonical.com [91.189.94.204]) by ozlabs.org (Postfix) with ESMTP id 8A79BB7016 for ; Mon, 25 Jun 2012 19:55:55 +1000 (EST) Received: from localhost ([127.0.0.1] helo=chlorine.canonical.com) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1Sj61K-0005rw-Kn; Mon, 25 Jun 2012 09:55:46 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1Sj61B-0005o0-FK for kernel-team@lists.ubuntu.com; Mon, 25 Jun 2012 09:55:37 +0000 Received: from p5b2e3468.dip.t-dialin.net ([91.46.52.104] helo=canonical.com) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1Sj61B-0004S6-A4 for kernel-team@lists.ubuntu.com; Mon, 25 Jun 2012 09:55:37 +0000 From: Stefan Bader To: kernel-team@lists.ubuntu.com Subject: [PATCH 2/2] UBUNTU: SAUCE: Use ticket locks for Xen 3.0.2+ Date: Mon, 25 Jun 2012 11:55:33 +0200 Message-Id: <1340618133-10755-3-git-send-email-stefan.bader@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1340618133-10755-1-git-send-email-stefan.bader@canonical.com> References: <1340618133-10755-1-git-send-email-stefan.bader@canonical.com> X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.13 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: kernel-team-bounces@lists.ubuntu.com Errors-To: kernel-team-bounces@lists.ubuntu.com The SUSE patchset did limit the ticket lock code to be used only on Xen hypervisors version 3.2 or higher because HYPERVISOR_poll() is supposed to have issues before. However we have been using that call before and the chance to be running on EC2 on such an old hypervisor is getting even less. Not using ticket locks and the hypervisor assisting could increase host cpu usage and unfairness in lock contention situations. BugLink: http://bugs.launchpad.net/bugs/929941 Signed-off-by: Stefan Bader --- arch/x86/include/mach-xen/asm/spinlock_types.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/mach-xen/asm/spinlock_types.h b/arch/x86/include/mach-xen/asm/spinlock_types.h index 7d01ae1..3fa1833 100644 --- a/arch/x86/include/mach-xen/asm/spinlock_types.h +++ b/arch/x86/include/mach-xen/asm/spinlock_types.h @@ -13,7 +13,7 @@ typedef union { /* * Xen versions prior to 3.2.x have a race condition with HYPERVISOR_poll(). */ -#if CONFIG_XEN_COMPAT >= 0x030200 +#if CONFIG_XEN_COMPAT >= 0x030002 /* * On Xen we support a single level of interrupt re-enabling per lock. Hence * we can have twice as many outstanding tickets. Thus the cut-off for using