linux/fs/befs
Nick Piggin fa0d7e3de6 fs: icache RCU free inodes
RCU free the struct inode. This will allow:

- Subsequent store-free path walking patch. The inode must be consulted for
  permissions when walking, so an RCU inode reference is a must.
- sb_inode_list_lock to be moved inside i_lock because sb list walkers who want
  to take i_lock no longer need to take sb_inode_list_lock to walk the list in
  the first place. This will simplify and optimize locking.
- Could remove some nested trylock loops in dcache code
- Could potentially simplify things a bit in VM land. Do not need to take the
  page lock to follow page->mapping.

The downsides of this is the performance cost of using RCU. In a simple
creat/unlink microbenchmark, performance drops by about 10% due to inability to
reuse cache-hot slab objects. As iterations increase and RCU freeing starts
kicking over, this increases to about 20%.

In cases where inode lifetimes are longer (ie. many inodes may be allocated
during the average life span of a single inode), a lot of this cache reuse is
not applicable, so the regression caused by this patch is smaller.

The cache-hot regression could largely be avoided by using SLAB_DESTROY_BY_RCU,
however this adds some complexity to list walking and store-free path walking,
so I prefer to implement this at a later date, if it is shown to be a win in
real situations. I haven't found a regression in any non-micro benchmark so I
doubt it will be a problem.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:26 +11:00
..
befs_fs_types.h befs: annotate fs32 on tests for superblock endianness 2008-10-16 11:21:46 -07:00
befs.h
btree.c
btree.h
ChangeLog
datastream.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
datastream.h
debug.c kmemtrace, befs: fix slab.h dependency problem 2009-04-03 12:21:33 +02:00
endian.h byteorder: don't directly include linux/byteorder/generic.h 2008-05-16 12:01:45 -07:00
inode.c
inode.h
io.c
io.h
Kconfig fs/Kconfig: move befs out 2009-01-22 13:15:57 +03:00
linuxvfs.c fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
Makefile
super.c befs: fix build on parisc 2009-04-08 10:21:43 -07:00
super.h
TODO