Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752024Ab0BHNdN (ORCPT ); Mon, 8 Feb 2010 08:33:13 -0500 Received: from mail-ew0-f228.google.com ([209.85.219.228]:46940 "EHLO mail-ew0-f228.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751744Ab0BHNdM (ORCPT ); Mon, 8 Feb 2010 08:33:12 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:content-type :content-transfer-encoding; b=nv6m1lFP42gCNOfaZQbIGAgQX02aPXV7FyO/rYc1EPFe/BfKxv1EUAzc0k+li44UkB D3K8m807rDABcYi/aGBDcM78ECXYaATDAHCxwlvm7U5dhMqWRo8bugYAC/QlVAL9Tgct Zw1pP7JJTL9si0Jp397wg9/t8dJ3PPoprN5+0= Message-ID: <4B701292.3030108@gmail.com> Date: Mon, 08 Feb 2010 14:33:06 +0100 From: Artur Skawina User-Agent: Thunderbird 2.0.0.22pre (X11/20090422) MIME-Version: 1.0 To: Michael Breuer CC: Linux Kernel Mailing List , Mike Galbraith , Arjan van de Ven , Joerg Roedel Subject: Re: x86 - cpu_relax - why nop vs. pause? References: <4B6EF853.9090704@majjas.com> <1265566470.6280.10.camel@marge.simson.net> <4B6F1DAE.6020407@majjas.com> <4B6F2D59.1070508@majjas.com> <4B6F8A02.2060006@majjas.com> In-Reply-To: <4B6F8A02.2060006@majjas.com> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 759 Lines: 15 Michael Breuer wrote: > Just to move away from this... totally perplexed, I retested a bit. > Seems something else had gone wrong causing me to try 'rep;pause' vs. > 'pause'. The resulting opcode is f3 f3 90, as noted above. > > I do see what seems to be a small but noticeable performance improvement > - no idea if there's a downside, and also no idea what f3 f3 90 does vs. > f3 90. Might be something interesting, or maybe not. Alignment? IOW what happens if you use eg "nop; rep; nop;" or "rep; nop; nop;"? -- 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/