diff options
author | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 01:49:49 -0500 |
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committer | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 01:50:26 -0500 |
commit | fa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9 (patch) | |
tree | 203e0f73883e4c26b5597e36042386a1237dab35 /fs/fat/inode.c | |
parent | 77812a1ef139d84270d27faacc0630c887411013 (diff) |
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>
Diffstat (limited to 'fs/fat/inode.c')
-rw-r--r-- | fs/fat/inode.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/fat/inode.c b/fs/fat/inode.c index ad6998a92c30..8cccfebee180 100644 --- a/fs/fat/inode.c +++ b/fs/fat/inode.c | |||
@@ -514,11 +514,18 @@ static struct inode *fat_alloc_inode(struct super_block *sb) | |||
514 | return &ei->vfs_inode; | 514 | return &ei->vfs_inode; |
515 | } | 515 | } |
516 | 516 | ||
517 | static void fat_destroy_inode(struct inode *inode) | 517 | static void fat_i_callback(struct rcu_head *head) |
518 | { | 518 | { |
519 | struct inode *inode = container_of(head, struct inode, i_rcu); | ||
520 | INIT_LIST_HEAD(&inode->i_dentry); | ||
519 | kmem_cache_free(fat_inode_cachep, MSDOS_I(inode)); | 521 | kmem_cache_free(fat_inode_cachep, MSDOS_I(inode)); |
520 | } | 522 | } |
521 | 523 | ||
524 | static void fat_destroy_inode(struct inode *inode) | ||
525 | { | ||
526 | call_rcu(&inode->i_rcu, fat_i_callback); | ||
527 | } | ||
528 | |||
522 | static void init_once(void *foo) | 529 | static void init_once(void *foo) |
523 | { | 530 | { |
524 | struct msdos_inode_info *ei = (struct msdos_inode_info *)foo; | 531 | struct msdos_inode_info *ei = (struct msdos_inode_info *)foo; |