From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id qAL0MqWK227352 for ; Tue, 20 Nov 2012 18:22:52 -0600 Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by cuda.sgi.com with ESMTP id 4gGnJ79U5m57CFDh (version=TLSv1 cipher=AES256-SHA bits=256 verify=NO) for ; Tue, 20 Nov 2012 16:25:01 -0800 (PST) Date: Wed, 21 Nov 2012 01:24:59 +0100 From: Jan Kara Subject: Re: [PATCH] xfs: Don't flush inodes when project quota exceeded Message-ID: <20121121002459.GA10507@quack.suse.cz> References: <1352766973-14197-1-git-send-email-jack@suse.cz> <20121119213913.GB29498@quack.suse.cz> <20121120000428.GZ14281@dastard> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20121120000428.GZ14281@dastard> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: Jan Kara , xfs@oss.sgi.com On Tue 20-11-12 11:04:28, Dave Chinner wrote: > On Mon, Nov 19, 2012 at 10:39:13PM +0100, Jan Kara wrote: > > On Tue 13-11-12 01:36:13, Jan Kara wrote: > > > When project quota gets exceeded xfs_iomap_write_delay() ends up flushing > > > inodes because ENOSPC gets returned from xfs_bmapi_delay() instead of EDQUOT. > > > This makes handling of writes over project quota rather slow as a simple test > > > program shows: > > > fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0644); > > > for (i = 0; i < 50000; i++) > > > pwrite(fd, buf, 4096, i*4096); > > > > > > Writing 200 MB like this into a directory with 100 MB project quota takes > > > around 6 minutes while it takes about 2 seconds with this patch applied. This > > > actually happens in a real world load when nfs pushes data into a directory > > > which is over project quota. > > > > > > Fix the problem by replacing XFS_QMOPT_ENOSPC flag with XFS_QMOPT_EPDQUOT. > > > That makes xfs_trans_reserve_quota_bydquots() return new error EPDQUOT when > > > project quota is exceeded. xfs_bmapi_delay() then uses this flag so that > > > xfs_iomap_write_delay() can distinguish real ENOSPC (requiring flushing) > > > from exceeded project quota (not requiring flushing). > > > > > > As a side effect this patch fixes inconsistency where e.g. xfs_create() > > > returned EDQUOT even when project quota was exceeded. > > Ping? Any opinions? > > FWIW, it doesn't look like it'll apply to a current XFs tree: > > > > @@ -441,8 +442,11 @@ retry: > > > */ > > > if (nimaps == 0) { > > > trace_xfs_delalloc_enospc(ip, offset, count); > > > - if (flushed) > > > - return XFS_ERROR(error ? error : ENOSPC); > > > + if (flushed) { > > > + if (error == 0 || error == EPDQUOT) > > > + error = ENOSPC; > > > + return XFS_ERROR(error); > > > + } > > > > > > if (error == ENOSPC) { > > > xfs_iunlock(ip, XFS_ILOCK_EXCL); > > This xfs_iomap_write_delay() looks like this now: > > /* > * If bmapi returned us nothing, we got either ENOSPC or EDQUOT. Retry > * without EOF preallocation. > */ > if (nimaps == 0) { > trace_xfs_delalloc_enospc(ip, offset, count); > if (prealloc) { > prealloc = 0; > error = 0; > goto retry; > } > return XFS_ERROR(error ? error : ENOSPC); > } > > The flushing is now way up in xfs_file_buffered_aio_write(), and the > implementation of xfs_flush_inodes() has changed as well. Hence it > may or may not behave differently not.... OK, so I tested latest XFS tree and changes by commit 9aa05000 (changing xfs_flush_inodes()) indeed improve the performace from those ~6 minutes to ~6 seconds which is good enough I believe. Thanks for the pointer! I was thinking for a while why sync_inodes_sb() is so much faster than the original XFS implementation and I believe it's because we don't force the log on each sync now. Honza -- Jan Kara SUSE Labs, CR _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs