From: Ric Wheeler Subject: Re: large file system & high object count testing Date: Mon, 31 Aug 2009 17:02:51 -0400 Message-ID: <4A9C3A7B.3050302@redhat.com> References: <4A9BFB88.5030409@redhat.com> <4A9C0220.1040503@redhat.com> <20090831205608.GE4197@webber.adilger.int> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-ext4@vger.kernel.org, "Ted Ts'o" To: Andreas Dilger Return-path: Received: from mx1.redhat.com ([209.132.183.28]:4636 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751605AbZHaVB2 (ORCPT ); Mon, 31 Aug 2009 17:01:28 -0400 In-Reply-To: <20090831205608.GE4197@webber.adilger.int> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 08/31/2009 04:56 PM, Andreas Dilger wrote: > On Aug 31, 2009 13:02 -0400, Ric Wheeler wrote: >> One more note - this file system was filled using fs_mark, but without >> doing any fsync() calls. >> >> umount: >> >> Aug 31 10:19:27 megadeth kernel: EXT4-fs: mballoc: 2580708130 blocks >> 516141626 reqs (511081408 success) >> Aug 31 10:19:27 megadeth kernel: EXT4-fs: mballoc: 5060218 extents >> scanned, 0 goal hits, 5060218 2^N hits, 0 breaks, 0 lost >> Aug 31 10:19:27 megadeth kernel: EXT4-fs: mballoc: 85164 generated and >> it took 471527376 >> Aug 31 10:19:27 megadeth kernel: EXT4-fs: mballoc: 2590831616 >> preallocated, 10120312 discarded >> >> Mount after fsck: >> Aug 31 12:27:12 megadeth kernel: EXT4-fs (dm-75): >> ext4_check_descriptors: Checksum for group 487 failed (59799!=46827) >> Aug 31 12:27:12 megadeth kernel: EXT4-fs (dm-75): group descriptors >> corrupted! >> >> The MBALLOC messages are a bit worrying - what exactly gets discarded >> during an unmount? > > The in-memory preallocation areas are discarded. This is reporting > that of the 2590M preallocation areas it reserved, only 10M of them > were discarded during the lifetime of the filesystem. > > Of the other stats: > - 471 seconds were spent in total generating the 85k buddy bitmaps > (this is done incrementally at runtime) > - 516M calls to mballoc to find a chunk of blocks, 511M calls were able > to find the requested chunk (not surprising given it is a new filesystem, > probably the 5M calls that failed were when the fs was nearly full) > > Cheers, Andreas > -- > Andreas Dilger > Sr. Staff Engineer, Lustre Group > Sun Microsystems of Canada, Inc. > This file system was never more than 7% full - the 511M calls were for each of the 20KB files more or less I guess. ric