From mboxrd@z Thu Jan 1 00:00:00 1970 From: liu weni Subject: Re: [PATCH 1/3]fs/inode: iunique() Optimize Performance Date: Tue, 1 Dec 2009 13:01:57 +0800 Message-ID: References: <200911252209432039291@gmail.com> <20091125141505.GH9482@parisc-linux.org> <20091125195256.GL9482@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: strongzgy , xgr178 , Liu Hui , viro , akpm , jack , npiggin , linux-fsdevel , linux-kernel To: Matthew Wilcox Return-path: Received: from mail-iw0-f171.google.com ([209.85.223.171]:44865 "EHLO mail-iw0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750815AbZLAFBw convert rfc822-to-8bit (ORCPT ); Tue, 1 Dec 2009 00:01:52 -0500 In-Reply-To: <20091125195256.GL9482@parisc-linux.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Thanks, I will try others way to improve the performance. 2009/11/26 Matthew Wilcox : > On Wed, Nov 25, 2009 at 08:20:02PM +0100, J?r?my Cochoy wrote: >> Hello, >> >> There is something strange in iunique : what will happend if all ino= de >> between max_reserved+1 and (unsinged in)(0-1) ? Will it make an >> infinite loop or an interruption can happen and make an inode become >> free? > > Another process can free an inode while this loop is executing. > >> In that case, it will be better to stop search when counter overflow= , no? > > If you have all four billion inodes allocated, you have significantly > bigger problems than this loop. =A0For a start, at 600 bytes per inod= e, > I'd like to see your machine with 2.4TB of memory. =A0Then there's th= e > size of your inode hash, and the depth of the chains within it. > >> Will it not be better to use a field max_ino_used (in superblock, fo= r >> exemple) where we store the last inode allocated with iunique and ma= ke >> a search only if max_ino_used become to (unsigned)(-1) ? >> >> But, if iunique is here to provide a solution in order to generate >> unused inode in filesystem which have various inode number, it's >> better to use a list of used ino, in a short hash table which use th= e >> first 8 bits of the inode, always use the same function to create a >> new inode and look at the head if we can add a new inode with bigger >> ino and still in the range. (But i think filesystems developper pref= er >> to write ther own functions in order to do that, no?) >> >> Well, if we want to stop in case of full inode filesystem, we can pu= t >> the first condition in the head and add change return as : >> return inode->i_ino > max_reserved ? res : 0; // 0 might "i can't fi= nd >> an inode after max_reserved" > > Gloves. > > http://thedailywtf.com/Articles/The_Complicator_0x27_s_Gloves.aspx > > -- > Matthew Wilcox =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Int= el Open Source Technology Centre > "Bill, look, we understand that you're interested in selling us this > operating system, but compare it to ours. =A0We can't possibly take s= uch > a retrograde step." > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html