Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756477Ab0LMHh3 (ORCPT ); Mon, 13 Dec 2010 02:37:29 -0500 Received: from mtoichi14.ns.itscom.net ([219.110.2.184]:39002 "EHLO mtoichi14.ns.itscom.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752765Ab0LMHh2 (ORCPT ); Mon, 13 Dec 2010 02:37:28 -0500 From: "J. R. Okajima" Subject: Re: Big git diff speedup by avoiding x86 "fast string" memcmp To: Nick Piggin Cc: Linus Torvalds , linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org In-Reply-To: <20101213014553.GA6522@amd> References: <20101209070938.GA3949@amd> <19324.1291990997@jrobl> <20101213014553.GA6522@amd> Date: Mon, 13 Dec 2010 16:29:11 +0900 Message-ID: <9580.1292225351@jrobl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 695 Lines: 18 Nick Piggin: > It's not scaling but just single threaded performance. gcc turns memcmp > into rep cmp, which has quite a long latency, so it's not appripriate > for short strings. Honestly speaking I doubt how this 'long *' approach is effective (Of course it never means that your result (by 'char *') is doubtful). But is the "rep cmp has quite a long latency" issue generic for all x86 architecture, or Westmere system specific? J. R. Okajima -- 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/