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btrfs: account ticket size at add/delete time

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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@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Nikolay Borisov 2020-03-10 11:00:35 +02:00 committed by David Sterba
parent f8e6608180
commit db161806dc
2 changed files with 13 additions and 6 deletions
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12
fs/btrfs/space-info.c
View File

@ -389,6 +389,8 @@ again:
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 +786,12 @@ 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;
u64 to_reclaim = space_info->reclaim_size;
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);
avail = calc_available_free_space(fs_info, space_info,
BTRFS_RESERVE_FLUSH_ALL);
@ -1192,8 +1190,10 @@ 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);

7
fs/btrfs/space-info.h
View File

@ -54,6 +54,13 @@ struct btrfs_space_info {
struct list_head ro_bgs;
struct list_head priority_tickets;
struct list_head tickets;
/*
* Size of space that needs to be reclaimed in order to satisfy pending
* tickets
*/
u64 reclaim_size;
/*
* tickets_id just indicates the next ticket will be handled, so note
* it's not stored per ticket.