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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 /fs/hugetlbfs/inode.c
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 'fs/hugetlbfs/inode.c')
-rw-r--r--fs/hugetlbfs/inode.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index a5fe68189eed..9885082b470f 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -663,11 +663,18 @@ static struct inode *hugetlbfs_alloc_inode(struct super_block *sb)
663 return &p->vfs_inode; 663 return &p->vfs_inode;
664} 664}
665 665
666static void hugetlbfs_i_callback(struct rcu_head *head)
667{
668 struct inode *inode = container_of(head, struct inode, i_rcu);
669 INIT_LIST_HEAD(&inode->i_dentry);
670 kmem_cache_free(hugetlbfs_inode_cachep, HUGETLBFS_I(inode));
671}
672
666static void hugetlbfs_destroy_inode(struct inode *inode) 673static void hugetlbfs_destroy_inode(struct inode *inode)
667{ 674{
668 hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb)); 675 hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb));
669 mpol_free_shared_policy(&HUGETLBFS_I(inode)->policy); 676 mpol_free_shared_policy(&HUGETLBFS_I(inode)->policy);
670 kmem_cache_free(hugetlbfs_inode_cachep, HUGETLBFS_I(inode)); 677 call_rcu(&inode->i_rcu, hugetlbfs_i_callback);
671} 678}
672 679
673static const struct address_space_operations hugetlbfs_aops = { 680static const struct address_space_operations hugetlbfs_aops = {