From mboxrd@z Thu Jan 1 00:00:00 1970 From: Artem Bityutskiy Subject: Re: [PATCH 0/5] Per superblock shrinkers V2 Date: Fri, 28 May 2010 10:42:06 +0300 Message-ID: <1275032526.15516.83.camel@localhost> References: <1274777588-21494-1-git-send-email-david@fromorbit.com> <20100527133223.efa4740a.akpm@linux-foundation.org> Reply-To: dedekind1@gmail.com Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Cc: Dave Chinner , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, xfs@oss.sgi.com To: Andrew Morton Return-path: In-Reply-To: <20100527133223.efa4740a.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.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: >=20 > > This series reworks the filesystem shrinkers. We currently have a > > set of issues with the current filesystem shrinkers: > >=20 > > 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. >=20 > 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. --=20 Best Regards, Artem Bityutskiy (=D0=90=D1=80=D1=82=D1=91=D0=BC =D0=91=D0=B8=D1=82=D1=8E= =D1=86=D0=BA=D0=B8=D0=B9) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org