Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758170Ab0BRTHI (ORCPT ); Thu, 18 Feb 2010 14:07:08 -0500 Received: from terminus.zytor.com ([198.137.202.10]:43443 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752532Ab0BRTHG (ORCPT ); Thu, 18 Feb 2010 14:07:06 -0500 Message-ID: <4B7D8FA5.40901@zytor.com> Date: Thu, 18 Feb 2010 11:06:13 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.7) Gecko/20100120 Fedora/3.0.1-1.fc12 Thunderbird/3.0.1 MIME-Version: 1.0 To: Luca Barbieri CC: Andi Kleen , mingo@elte.hu, 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 References: <1266406962-17463-1-git-send-email-luca@luca-barbieri.com> <1266406962-17463-10-git-send-email-luca@luca-barbieri.com> <87eikj54wp.fsf@basil.nowhere.org> <20100218101156.GE5964@basil.fritz.box> <4B7D7060.1080908@zytor.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1103 Lines: 25 On 02/18/2010 10:49 AM, Luca Barbieri wrote: >> This really sounds like the wrong optimization. These functions aren't >> exactly all that complex in assembly (which would also allow them to be >> simple cli/do stuff/sti), and instead relying on gcc features which may >> or may not be well supported on x86 is inviting breakage down the line. >> >> That is particularly damaging, since the remaining 486-class users tend >> to be deeply embedded and thus we only find problems later. > > There is the downside of adding a whole 386/486-specific implementation. > > It's not too hard though, and if we don't care about 486 SMP, it may > be a better option. We don't care about 486 SMP. And yes, I think it is a better option. At least an assembly option, once implemented, will *stay* implemented and won't break due to some obscure gcc change. -hpa -- 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/