Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752397AbZLAOAh (ORCPT ); Tue, 1 Dec 2009 09:00:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751806AbZLAOAg (ORCPT ); Tue, 1 Dec 2009 09:00:36 -0500 Received: from palinux.external.hp.com ([192.25.206.14]:47445 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751320AbZLAOAg (ORCPT ); Tue, 1 Dec 2009 09:00:36 -0500 Date: Tue, 1 Dec 2009 07:00:41 -0700 From: Matthew Wilcox To: Liuweni Cc: strongzgy , xgr178 , Liu Hui , viro , akpm , jack , npiggin , linux-fsdevel , linux-kernel Subject: Re: Re: [PATCH 1/3]fs/inode: iunique() Optimize Performance Message-ID: <20091201140041.GW9482@parisc-linux.org> References: <20091201120337.GV9482@parisc-linux.org> <200912012115341872867@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200912012115341872867@gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1288 Lines: 32 On Tue, Dec 01, 2009 at 09:21:32PM +0800, Liuweni wrote: > Hi Matthew Wilcox: > I got the code note as the following. if there is no performance problem, > maybe the code note need update. > > > ------ > * BUGS: > * With a large number of inodes live on the file system this function > * currently becomes quite slow. > I don't believe that comment is correct. In any case, your optimisation wouldn't make a lick of difference to the speed; it's a single comparison in a loop which also calculates a hash, makes a function call, and walks the length of a hash chain. The old adage about debugging code, not comments applies here. Don't take somebody else's word for it that there's a performance problem here. Devise a test to demonstrate the performance problem. Otherwise, how will you know if you solved it? -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- 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/