From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: [PATCH 7/7 v2] ext4: reclaim extents from extent status tree Date: Fri, 18 Jan 2013 00:39:47 -0500 Message-ID: <20130118053947.GD13785@thunk.org> References: <1357901627-3068-1-git-send-email-wenqing.lz@taobao.com> <1357901627-3068-8-git-send-email-wenqing.lz@taobao.com> <20130118051921.GC13785@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, Jan kara , Zheng Liu To: Zheng Liu Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:44128 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750830Ab3ARFjy (ORCPT ); Fri, 18 Jan 2013 00:39:54 -0500 Content-Disposition: inline In-Reply-To: <20130118051921.GC13785@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Jan 18, 2013 at 12:19:21AM -0500, Theodore Ts'o wrote: > I'm a bit concerned we might be too aggressive, > because there are two ways that items can be freed from the > extent_status tree. One is if the inode is not used at all, and when > we release the inode, we'll drop all of the entries in the > extent_status_tree for that inode. The second way is via the shrinker > which we've registered. If we use the sb->s_op->free_cached_objects() approach, something like the following change to prune_super() in fs/super.c might address the above concern: diff --git a/fs/super.c b/fs/super.c index 12f1237..fb57bd2 100644 --- a/fs/super.c +++ b/fs/super.c @@ -80,6 +80,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc) if (sc->nr_to_scan) { int dentries; int inodes; + int fs_to_scan = 0; /* proportion the scan between the caches */ dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) / @@ -87,7 +88,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc) inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) / total_objects; if (fs_objects) - fs_objects = (sc->nr_to_scan * fs_objects) / + fs_to_scan = (sc->nr_to_scan * fs_objects) / total_objects; /* * prune the dcache first as the icache is pinned by it, then @@ -96,8 +97,23 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc) prune_dcache_sb(sb, dentries); prune_icache_sb(sb, inodes); - if (fs_objects && sb->s_op->free_cached_objects) { - sb->s_op->free_cached_objects(sb, fs_objects); + /* + * If as a result of pruning the icache, we released some + * of the fs_objects, give credit to the fact and + * reduce the number of fs objects that we should try + * to release. + */ + if (fs_to_scan) { + int fs_objects_now = sb->s_op->nr_cached_objects(sb); + + if (fs_objects_now < fs_objects) + fs_to_scan -= fs_objects - fs_objects_now; + if (fs_to_scan < 0) + fs_to_scan = 0; + } + + if (fs_to_scan && sb->s_op->free_cached_objects) { + sb->s_op->free_cached_objects(sb, fs_to_scan); fs_objects = sb->s_op->nr_cached_objects(sb); } total_objects = sb->s_nr_dentry_unused + What do folks think? - Ted