Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752466AbZKYOo6 (ORCPT ); Wed, 25 Nov 2009 09:44:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751363AbZKYOo5 (ORCPT ); Wed, 25 Nov 2009 09:44:57 -0500 Received: from fg-out-1718.google.com ([72.14.220.154]:43068 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750883AbZKYOo4 (ORCPT ); Wed, 25 Nov 2009 09:44:56 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=gaC2m1/c4+XfvxPAIwP/nxb3bHAyKFimu1C4JgzNuW8SdibsLj+qZaV5JLag3mvVvV wUogAThTrQM4ql0kVVbPHZ47OfjFMRUNoMzE9pOSENarVRj+swOjF4kmmeOSwI0lJcON Kl3WOJSVZO+pd5c+Yzl8MUjLBeUserH6OCOdQ= Date: Wed, 25 Nov 2009 22:45:39 +0800 From: =?utf-8?Q?Am=C3=A9rico?= Wang To: Matthew Wilcox Cc: Liuweni , linux-kernel , viro , akpm , jack , npiggin , linux-fsdevel , strongzgy , xgr178 , Liu Hui Subject: Re: [PATCH 2/3]fs/inode: iunique() Optimize Performance Message-ID: <20091125144539.GA3520@hack> References: <200911252212166092236@gmail.com> <20091125141727.GI9482@parisc-linux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091125141727.GI9482@parisc-linux.org> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1078 Lines: 28 On Wed, Nov 25, 2009 at 07:17:28AM -0700, Matthew Wilcox wrote: >On Wed, Nov 25, 2009 at 10:12:19PM +0800, Liuweni wrote: >> @@ -605,8 +605,8 @@ static unsigned long hash(struct super_block *sb, unsigned long hashval) >> { >> unsigned long tmp; >> >> - tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) / >> - L1_CACHE_BYTES; >> + tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) >> >> + L1_CACHE_SHIFT; >> tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> I_HASHBITS); >> return tmp & I_HASHMASK; >> } > >Have you compared the compiler output before/after your change? I'd be >amazed if GCC isn't able to optimise division-by-a-constant-power-of-two >into shift-by-constant. If a compiler can't do this nowadays, I'd consider it's a bug. -- Live like a child, think like the god. -- 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/