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authorNick Piggin <npiggin@kernel.dk>2011-01-07 01:49:49 -0500
committerNick Piggin <npiggin@kernel.dk>2011-01-07 01:50:26 -0500
commitfa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9 (patch)
tree203e0f73883e4c26b5597e36042386a1237dab35 /mm
parent77812a1ef139d84270d27faacc0630c887411013 (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 'mm')
-rw-r--r--mm/shmem.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index 47fdeeb9d636..5ee67c990602 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2415,13 +2415,20 @@ static struct inode *shmem_alloc_inode(struct super_block *sb)
2415 return &p->vfs_inode; 2415 return &p->vfs_inode;
2416} 2416}
2417 2417
2418static void shmem_i_callback(struct rcu_head *head)
2419{
2420 struct inode *inode = container_of(head, struct inode, i_rcu);
2421 INIT_LIST_HEAD(&inode->i_dentry);
2422 kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2423}
2424
2418static void shmem_destroy_inode(struct inode *inode) 2425static void shmem_destroy_inode(struct inode *inode)
2419{ 2426{
2420 if ((inode->i_mode & S_IFMT) == S_IFREG) { 2427 if ((inode->i_mode & S_IFMT) == S_IFREG) {
2421 /* only struct inode is valid if it's an inline symlink */ 2428 /* only struct inode is valid if it's an inline symlink */
2422 mpol_free_shared_policy(&SHMEM_I(inode)->policy); 2429 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2423 } 2430 }
2424 kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode)); 2431 call_rcu(&inode->i_rcu, shmem_i_callback);
2425} 2432}
2426 2433
2427static void init_once(void *foo) 2434static void init_once(void *foo)