From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: Re: Re: [PATCH 1/3]fs/inode: iunique() Optimize Performance Date: Tue, 1 Dec 2009 07:00:41 -0700 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 Cc: strongzgy , xgr178 , Liu Hui , viro , akpm , jack , npiggin , linux-fsdevel , linux-kernel To: Liuweni Return-path: Content-Disposition: inline In-Reply-To: <200912012115341872867@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org 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."