From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755961Ab0E1Hov (ORCPT ); Fri, 28 May 2010 03:44:51 -0400 Received: from smtp.nokia.com ([192.100.122.233]:39808 "EHLO mgw-mx06.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754162Ab0E1Hos (ORCPT ); Fri, 28 May 2010 03:44:48 -0400 Subject: Re: [PATCH 0/5] Per superblock shrinkers V2 From: Artem Bityutskiy Reply-To: dedekind1@gmail.com To: Andrew Morton Cc: Dave Chinner , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, xfs@oss.sgi.com In-Reply-To: <20100527133223.efa4740a.akpm@linux-foundation.org> References: <1274777588-21494-1-git-send-email-david@fromorbit.com> <20100527133223.efa4740a.akpm@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" Date: Fri, 28 May 2010 10:42:06 +0300 Message-ID: <1275032526.15516.83.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 (2.28.3-1.fc12) Content-Transfer-Encoding: 8bit X-OriginalArrivalTime: 28 May 2010 07:43:50.0812 (UTC) FILETIME=[839C25C0:01CAFE39] X-Nokia-AV: Clean Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2010-05-27 at 13:32 -0700, Andrew Morton wrote: > On Tue, 25 May 2010 18:53:03 +1000 > Dave Chinner wrote: > > > This series reworks the filesystem shrinkers. We currently have a > > set of issues with the current filesystem shrinkers: > > > > 1. There is an dependency between dentry and inode cache > > shrinking that is only implicitly defined by the order of > > shrinker registration. > > 2. The shrinkers need to walk the superblock list and pin > > the superblock to avoid unmount races with the sb going > > away. > > 3. The dentry cache uses per-superblock LRUs and proportions > > reclaim between all the superblocks which means we are > > doing breadth based reclaim. This means we touch every > > superblock for every shrinker call, and may only reclaim > > a single dentry at a time from a given superblock. > > 4. The inode cache has a global LRU, so it has different > > reclaim patterns to the dentry cache, despite the fact > > that the dentry cache is generally the only thing that > > pins inodes in memory. > > 5. Filesystems need to register their own shrinkers for > > caches and can't co-ordinate them with the dentry and > > inode cache shrinkers. > > Nice description, but... it never actually told us what the benefit of > the changes are. Presumably some undescribed workload had some > undescribed user-visible problem. But what was that workload, and what > was the user-visible problem, and how does the patch affect all this? For UBIFS it wwill give a benefit in terms of simpler UBIFS code - we now have to keep our own list of UBIFS superblocks, provide locking for it, and maintain. This is just extra burden. So the item 2 above will be useful for UBIFS. -- Best Regards, Artem Bityutskiy (Артём Битюцкий)