From 37c42524d6090644206ae6d310d7e830bd3ccb47 Mon Sep 17 00:00:00 2001 From: "Denis V. Lunev" Date: Tue, 16 Oct 2007 23:29:53 -0700 Subject: shrink_dcache_sb speedup This patch makes shrink_dcache_sb consistent with dentry pruning policy. On the first pass we iterate over dentry unused list and prepare some dentries for removal. However, since the existing code moves evicted dentries to the beginning of the LRU it can happen that fresh dentries from other superblocks will be inserted *before* our dentries. This can result in significant slowdown of shrink_dcache_sb(). Moreover, for virtual filesystems like unionfs which can call dput() during dentries kill existing code results in O(n^2) complexity. We observed 2 minutes shrink_dcache_sb() with only 35000 dentries. To avoid this effects we propose to isolate sb dentries at the end of LRU list. Signed-off-by: Denis V. Lunev Signed-off-by: Kirill Korotaev Signed-off-by: Andrey Mirkin Cc: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/dcache.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index 5cdd14e9585..42d290be0ac 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -553,18 +553,18 @@ void shrink_dcache_sb(struct super_block * sb) * superblock to the most recent end of the unused list. */ spin_lock(&dcache_lock); - list_for_each_safe(tmp, next, &dentry_unused) { + list_for_each_prev_safe(tmp, next, &dentry_unused) { dentry = list_entry(tmp, struct dentry, d_lru); if (dentry->d_sb != sb) continue; - list_move(tmp, &dentry_unused); + list_move_tail(tmp, &dentry_unused); } /* * Pass two ... free the dentries for this superblock. */ repeat: - list_for_each_safe(tmp, next, &dentry_unused) { + list_for_each_prev_safe(tmp, next, &dentry_unused) { dentry = list_entry(tmp, struct dentry, d_lru); if (dentry->d_sb != sb) continue; -- cgit v1.2.3