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authorNick Piggin <npiggin@kernel.dk>2011-01-07 17:49:49 +1100
committerNick Piggin <npiggin@kernel.dk>2011-01-07 17:50:26 +1100
commitfa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9 (patch)
tree203e0f73883e4c26b5597e36042386a1237dab35 /include
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 'include')
-rw-r--r--include/linux/fs.h5
-rw-r--r--include/linux/net.h1
2 files changed, 4 insertions, 2 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 296cf2fde94..1ff4d0a33b2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -737,7 +737,10 @@ struct inode {
struct list_head i_wb_list; /* backing dev IO list */
struct list_head i_lru; /* inode LRU list */
struct list_head i_sb_list;
- struct list_head i_dentry;
+ union {
+ struct list_head i_dentry;
+ struct rcu_head i_rcu;
+ };
unsigned long i_ino;
atomic_t i_count;
unsigned int i_nlink;
diff --git a/include/linux/net.h b/include/linux/net.h
index 16faa130088..06bde490847 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -120,7 +120,6 @@ enum sock_shutdown_cmd {
struct socket_wq {
wait_queue_head_t wait;
struct fasync_struct *fasync_list;
- struct rcu_head rcu;
} ____cacheline_aligned_in_smp;
/**