From patchwork Mon Oct 21 16:05:08 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Raghavendra K T X-Patchwork-Id: 3078761 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 789EABF924 for ; Mon, 21 Oct 2013 16:07:11 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id D2B8320257 for ; Mon, 21 Oct 2013 16:07:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 34FE12021C for ; Mon, 21 Oct 2013 16:07:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751230Ab3JUQGo (ORCPT ); Mon, 21 Oct 2013 12:06:44 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:58650 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750898Ab3JUQGn (ORCPT ); Mon, 21 Oct 2013 12:06:43 -0400 Received: from /spool/local by e7.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 21 Oct 2013 12:06:41 -0400 Received: from d01dlp02.pok.ibm.com (9.56.250.167) by e7.ny.us.ibm.com (192.168.1.107) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Mon, 21 Oct 2013 12:06:38 -0400 Received: from b01cxnp22034.gho.pok.ibm.com (b01cxnp22034.gho.pok.ibm.com [9.57.198.24]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id BBB256E806F; Mon, 21 Oct 2013 12:06:33 -0400 (EDT) Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by b01cxnp22034.gho.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r9LG6X7I59506906; Mon, 21 Oct 2013 16:06:33 GMT Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r9LG6WAw016283; Mon, 21 Oct 2013 12:06:33 -0400 Received: from kernel.stglabs.ibm.com (kernel.stglabs.ibm.com [9.114.214.19]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id r9LG6Vdr016200; Mon, 21 Oct 2013 12:06:32 -0400 Received: from codeblue.in.ibm.com (unknown [9.79.183.181]) by kernel.stglabs.ibm.com (Postfix) with SMTP id 965D12401EF; Mon, 21 Oct 2013 09:06:27 -0700 (PDT) From: Raghavendra K T To: , , , , , Cc: , , , , Raghavendra K T Subject: [PATCH] x86 kconfig: Add recommendation to enable paravirt spinlock Date: Mon, 21 Oct 2013 21:35:08 +0530 Message-Id: <1382371508-3843-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.11.7 In-Reply-To: References: X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13102116-5806-0000-0000-00002327CA77 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-7.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Since paravirt spinlock optimization are in 3.12 kernel, we have very good performance benefit for paravirtualized KVM / Xen kernel. Also we no longer suffer from 5% side effect on native kernel. Signed-off-by: Raghavendra K T --- Would like to thank Sander for spotting and suggesting this. pvspinlock benefit on KVM link: https://lkml.org/lkml/2013/8/6/178 Attilio's tests on native kernel impact: http://blog.xen.org/index.php/2012/05/11/benchmarking-the-new-pv-ticketlock-implementation/ arch/x86/Kconfig | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f67e839..4ba9d32 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -638,10 +638,10 @@ config PARAVIRT_SPINLOCKS spinlock implementation with something virtualization-friendly (for example, block the virtual CPU rather than spinning). - Unfortunately the downside is an up to 5% performance hit on - native kernels, with various workloads. + It has minimal impact on native kernels and gives nice performance + benefit for paravirtualized KVM / Xen kernels. - If you are unsure how to answer this question, answer N. + If you are unsure how to answer this question, answer Y. source "arch/x86/xen/Kconfig"