linux/fs/coda
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
..
cache.c fs: dcache remove dcache_lock 2011-01-07 17:50:23 +11:00
cnode.c Coda: add spin lock to protect accesses to struct coda_inode_info. 2010-10-25 08:02:40 -07:00
coda_int.h drop unused dentry argument to ->fsync 2010-05-27 22:05:02 -04:00
coda_linux.c coda: remove CODA_FS_OLD_API 2008-07-25 10:53:33 -07:00
dir.c fs: dcache scale dentry refcount 2011-01-07 17:50:21 +11:00
file.c Coda: push BKL regions into coda_upcall() 2010-10-25 08:02:40 -07:00
inode.c fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
Kconfig fs/Kconfig: move coda out 2009-01-22 13:16:01 +03:00
Makefile Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pioctl.c Coda: push BKL regions into coda_upcall() 2010-10-25 08:02:40 -07:00
psdev.c Coda: replace BKL with mutex 2010-10-25 08:02:40 -07:00
symlink.c Coda: push BKL regions into coda_upcall() 2010-10-25 08:02:40 -07:00
sysctl.c sysctl: Drop & in front of every proc_handler. 2009-11-18 08:37:40 -08:00
upcall.c Coda: replace BKL with mutex 2010-10-25 08:02:40 -07:00