From: OGAWA Hirofumi Subject: Re: [PATCH V8 1/8] mm/fs: cleancache documentation Date: Sat, 16 Apr 2011 03:54:39 +0900 Message-ID: <87mxjr4a6o.fsf@devron.myhome.or.jp> References: <20110414211601.GA27691@ca-server1.us.oracle.com> Mime-Version: 1.0 Content-Type: text/plain Cc: chris.mason@oracle.com, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, adilger.kernel@dilger.ca, tytso@mit.edu, mfasheh@suse.com, jlbec@evilplan.org, matthew@wil.cx, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, ocfs2-devel@oss.oracle.com, linux-mm@kvack.org, hch@infradead.org, ngupta@vflare.org, jeremy@goop.org, JBeulich@novell.com, kurt.hackel@oracle.com, npiggin@kernel.dk, dave.mccracken@oracle.com, riel@redhat.com, avi@redhat.com, konrad.wilk@oracle.com, mel@csn.ul.ie, yinghan@google.com, gthelen@google.com, torvalds@linux-foundation.org To: Dan Magenheimer Return-path: In-Reply-To: <20110414211601.GA27691@ca-server1.us.oracle.com> (Dan Magenheimer's message of "Thu, 14 Apr 2011 14:16:01 -0700") Sender: owner-linux-mm@kvack.org List-Id: linux-ext4.vger.kernel.org Dan Magenheimer writes: > [PATCH V8 1/8] mm/fs: cleancache documentation > > This patchset introduces cleancache, an optional new feature exposed > by the VFS layer that potentially dramatically increases page cache > effectiveness for many workloads in many environments at a negligible > cost. It does this by providing an interface to transcendent memory, > which is memory/storage that is not otherwise visible to and/or directly > addressable by the kernel. > > Instead of being discarded, hooks in the reclaim code "put" clean > pages to cleancache. Filesystems that "opt-in" may "get" pages > from cleancache that were previously put, but pages in cleancache are > "ephemeral", meaning they may disappear at any time. And the size > of cleancache is entirely dynamic and unknowable to the kernel. > Filesystems currently supported by this patchset include ext3, ext4, > btrfs, and ocfs2. Other filesystems (especially those built entirely > on VFS) should be easy to add, but should first be thoroughly tested to > ensure coherency. > > Details and a FAQ are provided in Documentation/vm/cleancache.txt > > This first patch of eight in this cleancache series only adds two > new documentation files. Another question: why can't this enable/disable per sb, e.g. via mount options? (I have the interest the cache stuff like this by SSD on physical systems like dragonfly's swapcache.) Well, anyway, I guess force enabling this for mostly unused sb can just add cache-write overhead and call for unpleasing reclaim to backend (because of limited space of backend) like updatedb. And already there is in FAQ though, I also have interest about async interface because of SDD backend (I'm not sure for now though). Is there any plan like SSD backend? Thanks. -- OGAWA Hirofumi -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org