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author | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 17:49:49 +1100 |
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committer | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 17:50:26 +1100 |
commit | fa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9 (patch) | |
tree | 203e0f73883e4c26b5597e36042386a1237dab35 /fs/xfs | |
parent | 77812a1ef139d84270d27faacc0630c887411013 (diff) | |
download | op-kernel-dev-fa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9.zip op-kernel-dev-fa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9.tar.gz |
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/xfs')
-rw-r--r-- | fs/xfs/xfs_iget.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c index 0cdd269..d7de5a3 100644 --- a/fs/xfs/xfs_iget.c +++ b/fs/xfs/xfs_iget.c @@ -91,6 +91,17 @@ xfs_inode_alloc( return ip; } +STATIC void +xfs_inode_free_callback( + struct rcu_head *head) +{ + struct inode *inode = container_of(head, struct inode, i_rcu); + struct xfs_inode *ip = XFS_I(inode); + + INIT_LIST_HEAD(&inode->i_dentry); + kmem_zone_free(xfs_inode_zone, ip); +} + void xfs_inode_free( struct xfs_inode *ip) @@ -134,7 +145,7 @@ xfs_inode_free( ASSERT(!spin_is_locked(&ip->i_flags_lock)); ASSERT(completion_done(&ip->i_flush)); - kmem_zone_free(xfs_inode_zone, ip); + call_rcu(&ip->i_vnode.i_rcu, xfs_inode_free_callback); } /* |