diff options
author | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 01:49:49 -0500 |
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committer | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 01:50:26 -0500 |
commit | fa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9 (patch) | |
tree | 203e0f73883e4c26b5597e36042386a1237dab35 /fs/hugetlbfs/inode.c | |
parent | 77812a1ef139d84270d27faacc0630c887411013 (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.c | 9 |
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 | ||
666 | static 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 | |||
666 | static void hugetlbfs_destroy_inode(struct inode *inode) | 673 | static 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 | ||
673 | static const struct address_space_operations hugetlbfs_aops = { | 680 | static const struct address_space_operations hugetlbfs_aops = { |