Messages in this thread Patch in this message | | | From | Nick Piggin <> | Date | Sat, 27 Nov 2010 20:44:56 +1100 | Subject | [PATCH 26/46] fs: dcache reduce prune_one_dentry locking |
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prune_one_dentry can avoid quite a bit of locking in the common case where ancestors have an elevated refcount. Alternatively, we could have gone the other way and made fewer trylocks in the case where d_count goes to zero, but is probably less common.
Signed-off-by: Nick Piggin <npiggin@kernel.dk> --- fs/dcache.c | 27 +++++++++++++++------------ 1 files changed, 15 insertions(+), 12 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c index 23f6fed..4fa27b5 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -547,26 +547,29 @@ static void prune_one_dentry(struct dentry *dentry, struct dentry *parent) * Prune ancestors. */ while (dentry) { - spin_lock(&dcache_inode_lock); -again: +relock: spin_lock(&dentry->d_lock); + if (dentry->d_count > 1) { + dentry->d_count--; + spin_unlock(&dentry->d_lock); + return; + } + if (!spin_trylock(&dcache_inode_lock)) { +relock2: + spin_unlock(&dentry->d_lock); + cpu_relax(); + goto relock; + } + if (IS_ROOT(dentry)) parent = NULL; else parent = dentry->d_parent; if (parent && !spin_trylock(&parent->d_lock)) { - spin_unlock(&dentry->d_lock); - goto again; - } - dentry->d_count--; - if (dentry->d_count) { - if (parent) - spin_unlock(&parent->d_lock); - spin_unlock(&dentry->d_lock); spin_unlock(&dcache_inode_lock); - return; + goto relock2; } - + dentry->d_count--; dentry_lru_del(dentry); __d_drop(dentry); dentry = d_kill(dentry, parent); -- 1.7.1
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