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btrfs: avoid unnecessary wake ups on io trees when there are no waiters

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Whenever clearing the extent lock bits of an extent state record, we
unconditionally call wake_up() on the state's waitqueue. Most of the
time there are no waiters on the queue so we are just wasting time calling
wake_up(), since that requires locking and unlocking the queue's spinlock,
disable and re-enable interrupts, function calls, and other minor overhead
while we are holding a critical section delimited by the extent io tree's
spinlock.

So call wake_up() only if there are waiters on an extent state's wait
queue.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2026-03-11 15:07:11 +00:00 committed by David Sterba
parent d110eb2f7f
commit 87f5c3139e
1 changed files with 21 additions and 8 deletions
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29
fs/btrfs/extent-io-tree.c
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@ -536,6 +536,24 @@ static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
return 0;
}
static inline void state_wake_up(struct extent_io_tree *tree,
struct extent_state *state, u32 bits)
{
lockdep_assert_held(&tree->lock);
if (!(bits & EXTENT_LOCK_BITS))
return;
/*
* No memory barriers because the tree's lock is held while:
*
* 1) Adding waiters to the queue.
* 2) Waking up waiters.
* 3) Removing waiters from queue.
*/
cond_wake_up_nomb(&state->wq);
}
/*
* Use this during tree iteration to avoid doing next node searches when it's
* not needed (the current record ends at or after the target range's end).
@ -571,8 +589,7 @@ static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
if (unlikely(ret))
extent_io_tree_panic(tree, state, "add_extent_changeset", ret);
state->state &= ~bits_to_clear;
if (bits & EXTENT_LOCK_BITS)
wake_up(&state->wq);
state_wake_up(tree, state, bits);
if (state->state == 0) {
next = next_search_state(state, end);
if (extent_state_in_tree(state)) {
@ -618,7 +635,6 @@ int btrfs_clear_extent_bit_changeset(struct extent_io_tree *tree, u64 start, u64
u64 last_end;
int ret = 0;
bool clear;
bool wake;
const bool delete = (bits & EXTENT_CLEAR_ALL_BITS);
gfp_t mask;
@ -632,7 +648,6 @@ int btrfs_clear_extent_bit_changeset(struct extent_io_tree *tree, u64 start, u64
if (bits & EXTENT_DELALLOC)
bits |= EXTENT_NORESERVE;
wake = (bits & EXTENT_LOCK_BITS);
clear = (bits & (EXTENT_LOCK_BITS | EXTENT_BOUNDARY));
again:
if (!prealloc) {
@ -758,8 +773,7 @@ int btrfs_clear_extent_bit_changeset(struct extent_io_tree *tree, u64 start, u64
state->start = end + 1;
state->end = orig_end;
if (wake)
wake_up(&state->wq);
state_wake_up(tree, state, bits);
goto out;
}
@ -773,8 +787,7 @@ int btrfs_clear_extent_bit_changeset(struct extent_io_tree *tree, u64 start, u64
goto out;
}
if (wake)
wake_up(&state->wq);
state_wake_up(tree, state, bits);
clear_state_bit(tree, prealloc, bits, end, changeset);