Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423307AbXBPGGj (ORCPT ); Fri, 16 Feb 2007 01:06:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1423308AbXBPGGi (ORCPT ); Fri, 16 Feb 2007 01:06:38 -0500 Received: from smtp-outbound-1.vmware.com ([65.113.40.141]:44339 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423307AbXBPGGi (ORCPT ); Fri, 16 Feb 2007 01:06:38 -0500 Message-ID: <45D549ED.4000206@vmware.com> Date: Thu, 15 Feb 2007 22:06:37 -0800 From: Zachary Amsden User-Agent: Thunderbird 1.5.0.9 (X11/20061206) MIME-Version: 1.0 To: Jeremy Fitzhardinge CC: Andi Kleen , Andrew Morton , linux-kernel@vger.kernel.org, virtualization@lists.osdl.org, xen-devel@lists.xensource.com, Chris Wright , Ian Pratt , Christian Limpach Subject: Re: [patch 13/21] Xen-paravirt: Add nosegneg capability to the vsyscall page notes References: <20070216022449.739760547@goop.org> <20070216022531.495288020@goop.org> In-Reply-To: <20070216022531.495288020@goop.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1214 Lines: 27 Jeremy Fitzhardinge wrote: > Add the "nosegneg" fake capabilty to the vsyscall page notes. This is > used by the runtime linker to select a glibc version which then > disables negative-offset accesses to the thread-local segment via > %gs. These accesses require emulation in Xen (because segments are > truncated to protect the hypervisor address space) and avoiding them > provides a measurable performance boost. > > Signed-off-by: Ian Pratt > Signed-off-by: Christian Limpach > Signed-off-by: Chris Wright > Acked-by: Zachary Amsden We would like to see this by dynamic, but that is much more difficult to achieve, and seeing your recent linker issues, I don't think this should gate merging this code. The performance loss for us I believe to be negligible, and the fix is quite a bit more complicated than something achievable in the .21 timeframe. Zach - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/