From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Chen Subject: Re: system call time increase when turning on CONFIG_PARAVIRT Date: Wed, 07 Mar 2007 16:02:04 -0800 Message-ID: <1173312124.8383.35.camel@localhost.localdomain> References: <1172866274.4898.14.camel@localhost.localdomain> <45E89CFB.4090905@goop.org> <1172877111.8383.4.camel@localhost.localdomain> <45E8BE79.40200@goop.org> Reply-To: tim.c.chen@linux.intel.com Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <45E8BE79.40200@goop.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.osdl.org Errors-To: virtualization-bounces@lists.osdl.org To: Jeremy Fitzhardinge , zach@vmware.com Cc: Virtualization Mailing List , linux-kernel@vger.kernel.org List-Id: virtualization@lists.linuxfoundation.org On Fri, 2007-03-02 at 16:16 -0800, Jeremy Fitzhardinge wrote: > = > Yes, the intent is that running a CONFIG_PARAVIRT kernel on native > hardware will have negligible performance hit compared to running a > non-paravirt kernel. > = > J It turned out that VDSO was turned off by CONFIG_PARAVIRT option, causing the system call to use inefficient int 0x80 which led to the increase system_call time I was seeing. I noted that Ingo has caught this problem and proposed a patch to correct this issue in another mail thread. Tim From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751998AbXCHAxb (ORCPT ); Wed, 7 Mar 2007 19:53:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752151AbXCHAxb (ORCPT ); Wed, 7 Mar 2007 19:53:31 -0500 Received: from mga05.intel.com ([192.55.52.89]:9206 "EHLO fmsmga101.fm.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751998AbXCHAx3 (ORCPT ); Wed, 7 Mar 2007 19:53:29 -0500 X-ExtLoop1: 1 X-IronPort-AV: i="4.14,262,1170662400"; d="scan'208"; a="208423341:sNHT20280120" Subject: Re: system call time increase when turning on CONFIG_PARAVIRT From: Tim Chen Reply-To: tim.c.chen@linux.intel.com To: Jeremy Fitzhardinge , zach@vmware.com Cc: linux-kernel@vger.kernel.org, Virtualization Mailing List In-Reply-To: <45E8BE79.40200@goop.org> References: <1172866274.4898.14.camel@localhost.localdomain> <45E89CFB.4090905@goop.org> <1172877111.8383.4.camel@localhost.localdomain> <45E8BE79.40200@goop.org> Content-Type: text/plain Organization: Intel Date: Wed, 07 Mar 2007 16:02:04 -0800 Message-Id: <1173312124.8383.35.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 (2.0.2-8) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2007-03-02 at 16:16 -0800, Jeremy Fitzhardinge wrote: > > Yes, the intent is that running a CONFIG_PARAVIRT kernel on native > hardware will have negligible performance hit compared to running a > non-paravirt kernel. > > J It turned out that VDSO was turned off by CONFIG_PARAVIRT option, causing the system call to use inefficient int 0x80 which led to the increase system_call time I was seeing. I noted that Ingo has caught this problem and proposed a patch to correct this issue in another mail thread. Tim