From: Greg Freemyer Subject: Re: [PATCH 01/11 RESEND] libe2p: Add new function get_fragment_score() Date: Thu, 23 Jun 2011 07:16:20 -0400 Message-ID: References: <4DF8522F.2020304@sx.jp.nec.com> <20110617031814.GA31884@thunk.org> <4DFB62C7.5070008@redhat.com> <4E008045.1040909@sx.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Andreas Dilger , Eric Sandeen , "Ted Ts'o" , ext4 To: Kazuya Mio Return-path: Received: from mail-bw0-f46.google.com ([209.85.214.46]:64441 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752181Ab1FWLQw convert rfc822-to-8bit (ORCPT ); Thu, 23 Jun 2011 07:16:52 -0400 Received: by bwz15 with SMTP id 15so1429095bwz.19 for ; Thu, 23 Jun 2011 04:16:51 -0700 (PDT) In-Reply-To: <4E008045.1040909@sx.jp.nec.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Jun 21, 2011 at 7:28 AM, Kazuya Mio wrote= : > 2011/06/18 16:19, Andreas Dilger wrote: >> >> I was thinking about this, and am wondering if it makes sense to hav= e an >> absolute score for fragmentation >> instead of a relative one? >> >> By absolute I mean something like fragments per MB or similar. A bad= score >> might be anything> =A01. For >> files smaller than 1 MB in size it would scale the ratio to the equi= valent >> if the file was 1MB in size >> (e.g. a 16kB file with 4 fragments would have a score of 256, which = is >> clearly bad). =A0Large files can >> have a score much less than 1, which is good. > > I think fragments per MB is easy to understand. I will fix the librar= y > function > to "double e2p_get_fragscore(int fd)". To return fragments per MB, it= will > get the number of extents and the total length of extents except the > following > special cases: > - The extent whose initialize status is different from the next exten= t > - There is a hole between the extent and the next extent > - The extent is a tail =46or a sparse file, can you explain why you treat the head and tail extents of a block group differently? The issue is totally symetric in my mind, so either include both or exclude both in my opinion. The above description only excludes the block group tail extents. Greg -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html