[PATCH] btrfs: zoned: use greedy gc for auto reclaim
From: Johannes Thumshirn <hidden>
Date: 2021-10-11 11:11:51
Currently auto reclaim of unusable zones reclaims the block-groups in the order they have been added to the reclaim list. Change this to a greedy algorithm by sorting the list so we have the block-groups with the least amount of valid bytes reclaimed first. Signed-off-by: Johannes Thumshirn <redacted> --- Changes since RFC: - Updated the patch description - Don't sort the list under the spin_lock (David) --- fs/btrfs/block-group.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 46fdef7bbe20..930c07cdad81 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c@@ -1,5 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 +#include <linux/list_sort.h> + #include "misc.h" #include "ctree.h" #include "block-group.h"
@@ -1486,6 +1488,21 @@ void btrfs_mark_bg_unused(struct btrfs_block_group *bg) spin_unlock(&fs_info->unused_bgs_lock); } +/* + * We want block groups with a low number of used bytes to be in the beginning + * of the list, so they will get reclaimed first. + */ +static int reclaim_bgs_cmp(void *unused, const struct list_head *a, + const struct list_head *b) +{ + const struct btrfs_block_group *bg1, *bg2; + + bg1 = list_entry(a, struct btrfs_block_group, bg_list); + bg2 = list_entry(b, struct btrfs_block_group, bg_list); + + return bg1->used - bg2->used; +} + void btrfs_reclaim_bgs_work(struct work_struct *work) { struct btrfs_fs_info *fs_info =
@@ -1493,6 +1510,7 @@ void btrfs_reclaim_bgs_work(struct work_struct *work) struct btrfs_block_group *bg; struct btrfs_space_info *space_info; LIST_HEAD(again_list); + LIST_HEAD(reclaim_list); if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags)) return;
@@ -1510,17 +1528,20 @@ void btrfs_reclaim_bgs_work(struct work_struct *work) } spin_lock(&fs_info->unused_bgs_lock); - while (!list_empty(&fs_info->reclaim_bgs)) { + list_splice_init(&fs_info->reclaim_bgs, &reclaim_list); + spin_unlock(&fs_info->unused_bgs_lock); + + list_sort(NULL, &reclaim_list, reclaim_bgs_cmp); + while (!list_empty(&reclaim_list)) { u64 zone_unusable; int ret = 0; - bg = list_first_entry(&fs_info->reclaim_bgs, + bg = list_first_entry(&reclaim_list, struct btrfs_block_group, bg_list); list_del_init(&bg->bg_list); space_info = bg->space_info; - spin_unlock(&fs_info->unused_bgs_lock); /* Don't race with allocators so take the groups_sem */ down_write(&space_info->groups_sem);
@@ -1568,12 +1589,12 @@ void btrfs_reclaim_bgs_work(struct work_struct *work) bg->start); next: - spin_lock(&fs_info->unused_bgs_lock); if (ret == -EAGAIN && list_empty(&bg->bg_list)) list_add_tail(&bg->bg_list, &again_list); else btrfs_put_block_group(bg); } + spin_lock(&fs_info->unused_bgs_lock); list_splice_tail(&again_list, &fs_info->reclaim_bgs); spin_unlock(&fs_info->unused_bgs_lock); mutex_unlock(&fs_info->reclaim_bgs_lock);
--
2.32.0