From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Blunck Subject: Re: [patch 0/5] [PATCH,RFC] vfs: per-superblock unused dentries list (2nd version) Date: Mon, 19 Jun 2006 11:34:26 +0200 Message-ID: <20060619093426.GC6824@hasse.suse.de> References: <20060601095125.773684000@hasse.suse.de> <17539.35118.103025.716435@cse.unsw.edu.au> <20060616155120.GA6824@hasse.suse.de> <17555.12234.347353.670918@cse.unsw.edu.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, akpm@osdl.org, viro@zeniv.linux.org.uk, dgc@sgi.com, balbir@in.ibm.com Return-path: Received: from mx2.suse.de ([195.135.220.15]:55249 "EHLO mx2.suse.de") by vger.kernel.org with ESMTP id S932273AbWFSJe2 (ORCPT ); Mon, 19 Jun 2006 05:34:28 -0400 To: Neil Brown Content-Disposition: inline In-Reply-To: <17555.12234.347353.670918@cse.unsw.edu.au> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Sat, Jun 17, Neil Brown wrote: > But I cannot see that the whole LRU list needs to be scanned during > unmount. > The only thing that does that is shrink_dcache_sb, which is used: > in do_remount_sb > in __invalidate_device > in a few filesystems (autofs, coda, smbfs) > and not when unmounting the filesystem (despite the comment). > > (This is in 2.6.17-ec6-mm2). > > I can see that shrink_dcache_sb could take a long time and should be > fixed, which should be as simple as replacing it with > shrink_dcache_parent; shrink_dcache_anon. I don't remember exactly, maybe it was remounting instead of unmounting. Although I believe that we should call shrink_dcache_sb() instead of shrink_dcache_anon()+parent() when unmounting. I don't see any reason why we should shrink the dcache with depth-first traversal instead of just killing every unused dentry that we find (not even talking about that DCACHE_REFERENCE handling is nonesense in that case). > But I'm still puzzled as to why a long dcache LRU slows down > unmounting. > > Can you give more details? I think David already answered that. Jan