linux/fs/9p
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
..
acl.c fs/9p: Add access = client option to opt in acl evaluation. 2010-10-28 09:08:46 -05:00
acl.h fs/9p: Implement create time inheritance 2010-10-28 09:08:46 -05:00
cache.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
cache.h 9p: Add fscache support to 9p 2009-09-23 13:03:46 -05:00
fid.c fs/9p: Add access = client option to opt in acl evaluation. 2010-10-28 09:08:46 -05:00
fid.h 9p: Documentation updates 2008-05-14 19:23:25 -05:00
Kconfig fs/9p: Implement POSIX ACL permission checking function 2010-10-28 09:08:46 -05:00
Makefile fs/9p: Implement POSIX ACL permission checking function 2010-10-28 09:08:46 -05:00
v9fs_vfs.h 9p: Add datasync to client side TFSYNC/RFSYNC for dotl 2010-10-28 09:08:49 -05:00
v9fs.c fs/9p: Add access = client option to opt in acl evaluation. 2010-10-28 09:08:46 -05:00
v9fs.h 9p: Use V9FS_MAGIC in statfs 2010-10-28 09:08:47 -05:00
vfs_addr.c 9p: Add a Direct IO support for non-cached operations. 2010-10-28 09:08:45 -05:00
vfs_dentry.c fs: change d_delete semantics 2011-01-07 17:50:18 +11:00
vfs_dir.c 9p: Add datasync to client side TFSYNC/RFSYNC for dotl 2010-10-28 09:08:49 -05:00
vfs_file.c 9p: Add datasync to client side TFSYNC/RFSYNC for dotl 2010-10-28 09:08:49 -05:00
vfs_inode.c fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
vfs_super.c convert v9fs 2010-10-29 04:16:38 -04:00
xattr_user.c fs/9p: Add support user. xattr 2010-08-02 14:28:35 -05:00
xattr.c fs/9p: Add xattr callbacks for POSIX ACL 2010-10-28 09:08:46 -05:00
xattr.h fs/9p: Add xattr callbacks for POSIX ACL 2010-10-28 09:08:46 -05:00