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author | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 06:49:49 (GMT) |
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committer | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 06:50:26 (GMT) |
commit | fa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9 (patch) | |
tree | 203e0f73883e4c26b5597e36042386a1237dab35 /drivers/staging/pohmelfs | |
parent | 77812a1ef139d84270d27faacc0630c887411013 (diff) | |
download | linux-fa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9.tar.xz |
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 'drivers/staging/pohmelfs')
-rw-r--r-- | drivers/staging/pohmelfs/inode.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/staging/pohmelfs/inode.c b/drivers/staging/pohmelfs/inode.c index 61685cc..cc8d2840 100644 --- a/drivers/staging/pohmelfs/inode.c +++ b/drivers/staging/pohmelfs/inode.c @@ -826,6 +826,13 @@ const struct address_space_operations pohmelfs_aops = { .set_page_dirty = __set_page_dirty_nobuffers, }; +static void pohmelfs_i_callback(struct rcu_head *head) +{ + struct inode *inode = container_of(head, struct inode, i_rcu); + INIT_LIST_HEAD(&inode->i_dentry); + kmem_cache_free(pohmelfs_inode_cache, POHMELFS_I(inode)); +} + /* * ->detroy_inode() callback. Deletes inode from the caches * and frees private data. @@ -842,8 +849,8 @@ static void pohmelfs_destroy_inode(struct inode *inode) dprintk("%s: pi: %p, inode: %p, ino: %llu.\n", __func__, pi, &pi->vfs_inode, pi->ino); - kmem_cache_free(pohmelfs_inode_cache, pi); atomic_long_dec(&psb->total_inodes); + call_rcu(&inode->i_rcu, pohmelfs_i_callback); } /* |