Instead of iterating all pending tickets on the normal/priority list to
sum their total size the cost can be amortized across ticket addition/
removal. This turns O(n) + O(m) (where n is the size of the normal list
and m of the priority list) into O(1). This will mostly have effect in workloads
that experience heavy flushing.
Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
---
fs/btrfs/space-info.c | 13 ++++++++-----
fs/btrfs/space-info.h | 4 ++++
2 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 9cb511d8cd9d..316a724dc990 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -389,6 +389,8 @@ void btrfs_try_granting_tickets(struct btrfs_fs_info *fs_info,
space_info,
ticket->bytes);
list_del_init(&ticket->list);
+ ASSERT(space_info->reclaim_size >= ticket->bytes);
+ space_info->reclaim_size -= ticket->bytes;
ticket->bytes = 0;
space_info->tickets_id++;
wake_up(&ticket->wait);
@@ -784,16 +786,15 @@ static inline u64
btrfs_calc_reclaim_metadata_size(struct btrfs_fs_info *fs_info,
struct btrfs_space_info *space_info)
{
- struct reserve_ticket *ticket;
u64 used;
u64 avail;
u64 expected;
u64 to_reclaim = 0;
- list_for_each_entry(ticket, &space_info->tickets, list)
- to_reclaim += ticket->bytes;
- list_for_each_entry(ticket, &space_info->priority_tickets, list)
- to_reclaim += ticket->bytes;
+ lockdep_assert_held(&space_info->lock);
+
+ if (space_info->reclaim_size)
+ return space_info->reclaim_size;
avail = calc_available_free_space(fs_info, space_info,
BTRFS_RESERVE_FLUSH_ALL);
@@ -1192,8 +1193,10 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
* the list and we will do our own flushing further down.
*/
if (ret && flush != BTRFS_RESERVE_NO_FLUSH) {
+ ASSERT(space_info->reclaim_size >= 0);
ticket.bytes = orig_bytes;
ticket.error = 0;
+ space_info->reclaim_size += ticket.bytes;
init_waitqueue_head(&ticket.wait);
if (flush == BTRFS_RESERVE_FLUSH_ALL) {
list_add_tail(&ticket.list, &space_info->tickets);
diff --git a/fs/btrfs/space-info.h b/fs/btrfs/space-info.h
index 24514cd2c6c1..0e68a6dd2a79 100644
--- a/fs/btrfs/space-info.h
+++ b/fs/btrfs/space-info.h
@@ -54,6 +54,10 @@ struct btrfs_space_info {
struct list_head ro_bgs;
struct list_head priority_tickets;
struct list_head tickets;
+
+ u64 reclaim_size; /* Size of space that needs to be reclaimed in order
+ to satisfy pending tickets */
+
/*
* tickets_id just indicates the next ticket will be handled, so note
* it's not stored per ticket.
--
2.17.1
