Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=37c42524d6090644206ae6d310d7e830bd3ccb47
Commit: 37c42524d6090644206ae6d310d7e830bd3ccb47
Parent: 44a2db43eb715b54618bf01520cc5d46376cdbe2
Author: Denis V. Lunev <[EMAIL PROTECTED]>
AuthorDate: Tue Oct 16 23:29:53 2007 -0700
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Wed Oct 17 08:42:57 2007 -0700
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 <[EMAIL PROTECTED]>
Signed-off-by: Kirill Korotaev <[EMAIL PROTECTED]>
Signed-off-by: Andrey Mirkin <[EMAIL PROTECTED]>
Cc: Neil Brown <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
fs/dcache.c | 6 +++---
include/linux/list.h | 12 ++++++++++++
2 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 5cdd14e..42d290b 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;
diff --git a/include/linux/list.h b/include/linux/list.h
index ad9dcb9..b0cf013 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -478,6 +478,18 @@ static inline void list_splice_init_rcu(struct list_head
*list,
pos = n, n = pos->next)
/**
+ * list_for_each_prev_safe - iterate over a list backwards safe against removal
+ of list entry
+ * @pos: the &struct list_head to use as a loop cursor.
+ * @n: another &struct list_head to use as temporary storage
+ * @head: the head for your list.
+ */
+#define list_for_each_prev_safe(pos, n, head) \
+ for (pos = (head)->prev, n = pos->prev; \
+ prefetch(pos->prev), pos != (head); \
+ pos = n, n = pos->prev)
+
+/**
* list_for_each_entry - iterate over list of given type
* @pos: the type * to use as a loop cursor.
* @head: the head for your list.
-
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