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btrfs: only keep track of data extents for async discard

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As mentioned earlier, discarding data can be done either by issuing an
explicit discard or implicitly by reusing the LBA. Metadata block_groups
see much more frequent reuse due to well it being metadata. So instead
of explicitly discarding metadata block_groups, just leave them be and
let the latter implicit discarding be done for them.

For mixed block_groups, block_groups which contain both metadata and
data, we let them be as higher fragmentation is expected.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Dennis Zhou 2020-01-02 16:26:40 -05:00 committed by David Sterba
parent 7fe6d45e40
commit 5cb0724e1b
2 changed files with 21 additions and 2 deletions
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11
fs/btrfs/block-group.h
View File

@ -182,6 +182,17 @@ static inline u64 btrfs_block_group_end(struct btrfs_block_group *block_group)
return (block_group->start + block_group->length);
}
static inline bool btrfs_is_block_group_data_only(
struct btrfs_block_group *block_group)
{
/*
* In mixed mode the fragmentation is expected to be high, lowering the
* efficiency, so only proper data block groups are considered.
*/
return (block_group->flags & BTRFS_BLOCK_GROUP_DATA) &&
!(block_group->flags & BTRFS_BLOCK_GROUP_METADATA);
}
#ifdef CONFIG_BTRFS_DEBUG
static inline int btrfs_should_fragment_free_space(
struct btrfs_block_group *block_group)

12
fs/btrfs/discard.c
View File

@ -57,6 +57,9 @@ static void __add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
static void add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
struct btrfs_block_group *block_group)
{
if (!btrfs_is_block_group_data_only(block_group))
return;
spin_lock(&discard_ctl->lock);
__add_to_discard_list(discard_ctl, block_group);
spin_unlock(&discard_ctl->lock);
@ -169,7 +172,10 @@ again:
if (block_group && now > block_group->discard_eligible_time) {
if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED &&
block_group->used != 0) {
__add_to_discard_list(discard_ctl, block_group);
if (btrfs_is_block_group_data_only(block_group))
__add_to_discard_list(discard_ctl, block_group);
else
list_del_init(&block_group->discard_list);
goto again;
}
if (block_group->discard_state == BTRFS_DISCARD_RESET_CURSOR) {
@ -507,7 +513,9 @@ void btrfs_discard_update_discardable(struct btrfs_block_group *block_group,
s32 extents_delta;
s64 bytes_delta;
if (!block_group || !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
if (!block_group ||
!btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC) ||
!btrfs_is_block_group_data_only(block_group))
return;
discard_ctl = &block_group->fs_info->discard_ctl;