Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933510AbXK2T1s (ORCPT ); Thu, 29 Nov 2007 14:27:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933379AbXK2T1Z (ORCPT ); Thu, 29 Nov 2007 14:27:25 -0500 Received: from one.firstfloor.org ([213.235.205.2]:52938 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933352AbXK2T1Y (ORCPT ); Thu, 29 Nov 2007 14:27:24 -0500 Date: Thu, 29 Nov 2007 20:27:21 +0100 From: Andi Kleen To: "H. Peter Anvin" Cc: Linus Torvalds , Andi Kleen , Chuck Ebbert , Roland McGrath , Andrew Morton , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Jeremy Fitzhardinge , zach@vmware.com Subject: Re: [PATCH x86/mm 6/6] x86-64 ia32 ptrace get/putreg32 current task Message-ID: <20071129192721.GP24223@one.firstfloor.org> References: <20071129003849.428E026F8E7@magilla.localdomain> <20071129004222.E49AD26F8E7@magilla.localdomain> <474EF824.3020806@redhat.com> <474F01F6.2030509@zytor.com> <474F08E1.2090806@zytor.com> <474F1027.2020801@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <474F1027.2020801@zytor.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 809 Lines: 18 On Thu, Nov 29, 2007 at 11:16:55AM -0800, H. Peter Anvin wrote: > Andi, do you happen to remember the details on this? x86-64 has to use GS because there is no SWAPFS We decided to make it opposite on user space back then, but not based on benchmarks (there were only simulators back then) Oh yes the reason was that the GS context switch is slightly more expensive than the FS one and the code does lazy optimization. For i386 iirc Jeremy/Zach did the benchmarking and they settled on %fs because it was faster for something (originally it was %gs too) -Andi - 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/