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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/ext4
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/ext4')
-rw-r--r--fs/ext4/super.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index fb15c9c0be74..cd37f9d5e447 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -841,6 +841,13 @@ static int ext4_drop_inode(struct inode *inode)
841 return drop; 841 return drop;
842} 842}
843 843
844static void ext4_i_callback(struct rcu_head *head)
845{
846 struct inode *inode = container_of(head, struct inode, i_rcu);
847 INIT_LIST_HEAD(&inode->i_dentry);
848 kmem_cache_free(ext4_inode_cachep, EXT4_I(inode));
849}
850
844static void ext4_destroy_inode(struct inode *inode) 851static void ext4_destroy_inode(struct inode *inode)
845{ 852{
846 ext4_ioend_wait(inode); 853 ext4_ioend_wait(inode);
@@ -853,7 +860,7 @@ static void ext4_destroy_inode(struct inode *inode)
853 true); 860 true);
854 dump_stack(); 861 dump_stack();
855 } 862 }
856 kmem_cache_free(ext4_inode_cachep, EXT4_I(inode)); 863 call_rcu(&inode->i_rcu, ext4_i_callback);
857} 864}
858 865
859static void init_once(void *foo) 866static void init_once(void *foo)