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authorDan Magenheimer <dan.magenheimer@oracle.com>2011-05-26 12:00:56 -0400
committerDan Magenheimer <dan.magenheimer@oracle.com>2011-05-26 12:00:56 -0400
commit4fe4746ab694690af9f2ccb80184f5c575917c7f (patch)
tree533cf28d9c926e6f684c3905286ab179c2b4cc88 /Documentation/ABI/testing
parent61c4f2c81c61f73549928dfd9f3e8f26aa36a8cf (diff)
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. [v8: minor documentation changes by author] [v3: akpm@linux-foundation.org: document sysfs API] [v3: hch@infradead.org: move detailed description to Documentation/vm] Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com> Reviewed-by: Jeremy Fitzhardinge <jeremy@goop.org> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Acked-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Randy Dunlap <randy.dunlap@oracle.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Matthew Wilcox <matthew@wil.cx> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Rik Van Riel <riel@redhat.com> Cc: Jan Beulich <JBeulich@novell.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Andreas Dilger <adilger@sun.com> Cc: Ted Ts'o <tytso@mit.edu> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <joel.becker@oracle.com> Cc: Nitin Gupta <ngupta@vflare.org>
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1What: /sys/kernel/mm/cleancache/
2Date: April 2011
3Contact: Dan Magenheimer <dan.magenheimer@oracle.com>
4Description:
5 /sys/kernel/mm/cleancache/ contains a number of files which
6 record a count of various cleancache operations
7 (sum across all filesystems):
8 succ_gets
9 failed_gets
10 puts
11 flushes