kernel_optimize_test/fs/udf
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
..
balloc.c udf: Remove dead quota code 2010-05-24 14:10:19 +02:00
dir.c rename the generic fsync implementations 2010-05-27 22:06:06 -04:00
directory.c udf: Remove dead code 2009-09-14 19:13:00 +02:00
ecma_167.h Remove struct typedefs from fs/udf/ecma_167.h et al. 2009-04-02 12:29:47 +02:00
file.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2010-08-10 11:26:52 -07:00
ialloc.c switch udf to ->evict_inode() 2010-08-09 16:48:19 -04:00
inode.c switch udf to ->evict_inode() 2010-08-09 16:48:19 -04:00
Kconfig BKL: introduce CONFIG_BKL. 2010-10-21 15:44:13 +02:00
lowlevel.c udf: Remove dead code 2009-09-14 19:13:00 +02:00
Makefile switch udf to simple_fsync() 2009-06-11 21:36:13 -04:00
misc.c Fix the udf code not to pass structs on stack where possible. 2009-04-02 12:29:47 +02:00
namei.c new helper: ihold() 2010-10-25 21:26:11 -04:00
osta_udf.h Remove struct typedefs from fs/udf/ecma_167.h et al. 2009-04-02 12:29:47 +02:00
partition.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
super.c fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
symlink.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
truncate.c Fix the udf code not to pass structs on stack where possible. 2009-04-02 12:29:47 +02:00
udf_i.h Remove struct typedefs from fs/udf/ecma_167.h et al. 2009-04-02 12:29:47 +02:00
udf_sb.h udf: Don't write integrity descriptor too often 2009-04-02 13:36:28 +02:00
udfdecl.h switch udf to ->evict_inode() 2010-08-09 16:48:19 -04:00
udfend.h Remove struct typedefs from fs/udf/ecma_167.h et al. 2009-04-02 12:29:47 +02:00
udftime.c Remove struct typedefs from fs/udf/ecma_167.h et al. 2009-04-02 12:29:47 +02:00
unicode.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