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authorChris Mason <chris.mason@oracle.com>2011-07-16 15:23:14 -0400
committerChris Mason <chris.mason@oracle.com>2011-07-27 12:46:46 -0400
commitbd681513fa6f2ff29aa391f01e413a2d1c59fd77 (patch)
treebb10ec6ef876b4d7a553cbe54976ec49a0d10b21 /fs/btrfs/extent-tree.c
parent81317fdeddcef259b6ecf7b5c0d04caa167c6b54 (diff)
downloadop-kernel-dev-bd681513fa6f2ff29aa391f01e413a2d1c59fd77.zip
op-kernel-dev-bd681513fa6f2ff29aa391f01e413a2d1c59fd77.tar.gz
Btrfs: switch the btrfs tree locks to reader/writer
The btrfs metadata btree is the source of significant lock contention, especially in the root node. This commit changes our locking to use a reader/writer lock. The lock is built on top of rw spinlocks, and it extends the lock tracking to remember if we have a read lock or a write lock when we go to blocking. Atomics count the number of blocking readers or writers at any given time. It removes all of the adaptive spinning from the old code and uses only the spinning/blocking hints inside of btrfs to decide when it should continue spinning. In read heavy workloads this is dramatically faster. In write heavy workloads we're still faster because of less contention on the root node lock. We suffer slightly in dbench because we schedule more often during write locks, but all other benchmarks so far are improved. Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/extent-tree.c')
-rw-r--r--fs/btrfs/extent-tree.c20
1 files changed, 10 insertions, 10 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 7021dde..2a782c2 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5912,7 +5912,7 @@ static noinline int walk_down_proc(struct btrfs_trans_handle *trans,
return 1;
if (path->locks[level] && !wc->keep_locks) {
- btrfs_tree_unlock(eb);
+ btrfs_tree_unlock_rw(eb, path->locks[level]);
path->locks[level] = 0;
}
return 0;
@@ -5936,7 +5936,7 @@ static noinline int walk_down_proc(struct btrfs_trans_handle *trans,
* keep the tree lock
*/
if (path->locks[level] && level > 0) {
- btrfs_tree_unlock(eb);
+ btrfs_tree_unlock_rw(eb, path->locks[level]);
path->locks[level] = 0;
}
return 0;
@@ -6049,7 +6049,7 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
BUG_ON(level != btrfs_header_level(next));
path->nodes[level] = next;
path->slots[level] = 0;
- path->locks[level] = 1;
+ path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
wc->level = level;
if (wc->level == 1)
wc->reada_slot = 0;
@@ -6120,7 +6120,7 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans,
BUG_ON(level == 0);
btrfs_tree_lock(eb);
btrfs_set_lock_blocking(eb);
- path->locks[level] = 1;
+ path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
ret = btrfs_lookup_extent_info(trans, root,
eb->start, eb->len,
@@ -6129,8 +6129,7 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans,
BUG_ON(ret);
BUG_ON(wc->refs[level] == 0);
if (wc->refs[level] == 1) {
- btrfs_tree_unlock(eb);
- path->locks[level] = 0;
+ btrfs_tree_unlock_rw(eb, path->locks[level]);
return 1;
}
}
@@ -6152,7 +6151,7 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans,
btrfs_header_generation(eb) == trans->transid) {
btrfs_tree_lock(eb);
btrfs_set_lock_blocking(eb);
- path->locks[level] = 1;
+ path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
}
clean_tree_block(trans, root, eb);
}
@@ -6231,7 +6230,8 @@ static noinline int walk_up_tree(struct btrfs_trans_handle *trans,
return 0;
if (path->locks[level]) {
- btrfs_tree_unlock(path->nodes[level]);
+ btrfs_tree_unlock_rw(path->nodes[level],
+ path->locks[level]);
path->locks[level] = 0;
}
free_extent_buffer(path->nodes[level]);
@@ -6283,7 +6283,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
path->nodes[level] = btrfs_lock_root_node(root);
btrfs_set_lock_blocking(path->nodes[level]);
path->slots[level] = 0;
- path->locks[level] = 1;
+ path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
memset(&wc->update_progress, 0,
sizeof(wc->update_progress));
} else {
@@ -6451,7 +6451,7 @@ int btrfs_drop_subtree(struct btrfs_trans_handle *trans,
level = btrfs_header_level(node);
path->nodes[level] = node;
path->slots[level] = 0;
- path->locks[level] = 1;
+ path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
wc->refs[parent_level] = 1;
wc->flags[parent_level] = BTRFS_BLOCK_FLAG_FULL_BACKREF;
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