Star64_linux/Documentation/filesystems
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
..
caching
configfs Documentation: make configfs example code simpler, clearer 2010-11-18 15:00:46 -08:00
nfs
pohmelfs
00-INDEX
9p.txt
adfs.txt
affs.txt
afs.txt
autofs4-mount-control.txt
automount-support.txt
befs.txt
bfs.txt
btrfs.txt
ceph.txt
cifs.txt
coda.txt
cramfs.txt
debugfs.txt
dentry-locking.txt fs: dcache remove dcache_lock 2011-01-07 17:50:23 +11:00
devpts.txt
directory-locking
dlmfs.txt
dnotify.txt
dnotify_test.c
ecryptfs.txt
exofs.txt
ext2.txt
ext3.txt
ext4.txt
fiemap.txt
files.txt
fuse.txt
gfs2-glocks.txt
gfs2-uevents.txt
gfs2.txt
hfs.txt
hfsplus.txt
hpfs.txt
inotify.txt
isofs.txt
jfs.txt
Locking fs: dcache remove dcache_lock 2011-01-07 17:50:23 +11:00
locks.txt
logfs.txt
Makefile
mandatory-locking.txt
ncpfs.txt
nilfs2.txt
ntfs.txt
ocfs2.txt
omfs.txt
porting fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
proc.txt
quota.txt
ramfs-rootfs-initramfs.txt
relay.txt
romfs.txt
seq_file.txt
sharedsubtree.txt
spufs.txt
squashfs.txt
sysfs-pci.txt
sysfs-tagging.txt
sysfs.txt
sysv-fs.txt
tmpfs.txt
ubifs.txt
udf.txt
ufs.txt
vfat.txt
vfs.txt fs: change d_hash for rcu-walk 2011-01-07 17:50:20 +11:00
xfs-delayed-logging-design.txt xfs: remove experimental tag from the delaylog option 2010-11-10 12:00:47 -06:00
xfs.txt
xip.txt