From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753133Ab0BRIXL (ORCPT ); Thu, 18 Feb 2010 03:23:11 -0500 Received: from one.firstfloor.org ([213.235.205.2]:33058 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751623Ab0BRIXG (ORCPT ); Thu, 18 Feb 2010 03:23:06 -0500 To: Luca Barbieri Cc: mingo@elte.hu, hpa@zytor.com, a.p.zijlstra@chello.nl, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 09/10] x86-32: use SSE for atomic64_read/set if available From: Andi Kleen References: <1266406962-17463-1-git-send-email-luca@luca-barbieri.com> <1266406962-17463-10-git-send-email-luca@luca-barbieri.com> Date: Thu, 18 Feb 2010 09:23:02 +0100 In-Reply-To: <1266406962-17463-10-git-send-email-luca@luca-barbieri.com> (Luca Barbieri's message of "Wed, 17 Feb 2010 12:42:41 +0100") Message-ID: <87eikj54wp.fsf@basil.nowhere.org> User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/22.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Luca Barbieri writes: > This patch uses SSE movlps to perform 64-bit atomic reads and writes. You seem to have forgotten to add benchmark results that show this is actually worth while? And is there really any user on 32bit that needs 64bit atomic_t? I have to agree with Peter on it being a bad idea very likely to mess with FPU state like this. I'm also suspicious of your use of global register variables. This means they won't be saved on entry/exit of the functions. Does that really work? It's also a not widely used gcc feature and those are always somewhat risky. -Andi -- ak@linux.intel.com -- Speaking for myself only.