From f66e0209bd914465c277c259472aa974cad94e3f Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Thu, 28 Sep 2023 11:12:49 +0100 Subject: btrfs: stop reserving excessive space for block group item updates Space for block group item updates, necessary after allocating or deallocating an extent from a block group, is reserved in the delayed refs block reserve. Currently we do this by incrementing the transaction handle's delayed_ref_updates counter and then calling btrfs_update_delayed_refs_rsv(), which will increase the size of the delayed refs block reserve by an amount that corresponds to the same amount we use for delayed refs, given by btrfs_calc_delayed_ref_bytes(). That is an excessive amount because it corresponds to the amount of space needed to insert one item in a btree (btrfs_calc_insert_metadata_size()) times 2 when the free space tree feature is enabled. All we need is an amount as given by btrfs_calc_metadata_size(), since we only need to update an existing block group item in the extent tree (or block group tree if this feature is enabled). By using btrfs_calc_metadata_size() we will need to reserve 4 times less space when using the free space tree and 2 times less space when not using it, putting less pressure on space reservation. So use helpers to reserve and release space for block group item updates that use btrfs_calc_metadata_size() for calculation of the space. Signed-off-by: Filipe Manana Signed-off-by: David Sterba --- fs/btrfs/block-group.c | 12 +++++++----- fs/btrfs/delayed-ref.c | 35 +++++++++++++++++++++++++++++++++++ fs/btrfs/delayed-ref.h | 2 ++ fs/btrfs/disk-io.c | 2 +- 4 files changed, 45 insertions(+), 6 deletions(-) (limited to 'fs/btrfs') diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c index 6e2a4000bfe0..9d17b0580fbf 100644 --- a/fs/btrfs/block-group.c +++ b/fs/btrfs/block-group.c @@ -1286,7 +1286,7 @@ out: /* Once for the lookup reference */ btrfs_put_block_group(block_group); if (remove_rsv) - btrfs_delayed_refs_rsv_release(fs_info, 1, 0); + btrfs_dec_delayed_refs_rsv_bg_updates(fs_info); btrfs_free_path(path); return ret; } @@ -3369,7 +3369,7 @@ again: if (should_put) btrfs_put_block_group(cache); if (drop_reserve) - btrfs_delayed_refs_rsv_release(fs_info, 1, 0); + btrfs_dec_delayed_refs_rsv_bg_updates(fs_info); /* * Avoid blocking other tasks for too long. It might even save * us from writing caches for block groups that are going to be @@ -3516,7 +3516,7 @@ int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans) /* If its not on the io list, we need to put the block group */ if (should_put) btrfs_put_block_group(cache); - btrfs_delayed_refs_rsv_release(fs_info, 1, 0); + btrfs_dec_delayed_refs_rsv_bg_updates(fs_info); spin_lock(&cur_trans->dirty_bgs_lock); } spin_unlock(&cur_trans->dirty_bgs_lock); @@ -3545,6 +3545,7 @@ int btrfs_update_block_group(struct btrfs_trans_handle *trans, struct btrfs_block_group *cache; u64 old_val; bool reclaim = false; + bool bg_already_dirty = true; int factor; /* Block accounting for super block */ @@ -3613,7 +3614,7 @@ int btrfs_update_block_group(struct btrfs_trans_handle *trans, spin_lock(&trans->transaction->dirty_bgs_lock); if (list_empty(&cache->dirty_list)) { list_add_tail(&cache->dirty_list, &trans->transaction->dirty_bgs); - trans->delayed_ref_updates++; + bg_already_dirty = false; btrfs_get_block_group(cache); } spin_unlock(&trans->transaction->dirty_bgs_lock); @@ -3633,7 +3634,8 @@ int btrfs_update_block_group(struct btrfs_trans_handle *trans, btrfs_put_block_group(cache); /* Modified block groups are accounted for in the delayed_refs_rsv. */ - btrfs_update_delayed_refs_rsv(trans); + if (!bg_already_dirty) + btrfs_inc_delayed_refs_rsv_bg_updates(info); return 0; } diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c index 619d10eff0b4..de8434795913 100644 --- a/fs/btrfs/delayed-ref.c +++ b/fs/btrfs/delayed-ref.c @@ -125,6 +125,41 @@ void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans) trans->delayed_ref_csum_deletions = 0; } +/* + * Adjust the size of the delayed refs block reserve for 1 block group item + * update. + */ +void btrfs_inc_delayed_refs_rsv_bg_updates(struct btrfs_fs_info *fs_info) +{ + struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv; + + spin_lock(&delayed_rsv->lock); + /* + * Updating a block group item does not result in new nodes/leaves and + * does not require changing the free space tree, only the extent tree + * or the block group tree, so this is all we need. + */ + delayed_rsv->size += btrfs_calc_metadata_size(fs_info, 1); + delayed_rsv->full = false; + spin_unlock(&delayed_rsv->lock); +} + +/* + * Adjust the size of the delayed refs block reserve to release space for 1 + * block group item update. + */ +void btrfs_dec_delayed_refs_rsv_bg_updates(struct btrfs_fs_info *fs_info) +{ + struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv; + const u64 num_bytes = btrfs_calc_metadata_size(fs_info, 1); + u64 released; + + released = btrfs_block_rsv_release(fs_info, delayed_rsv, num_bytes, NULL); + if (released > 0) + trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv", + 0, released, 0); +} + /* * Transfer bytes to our delayed refs rsv. * diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h index 3b4f71dc30be..250e8742a136 100644 --- a/fs/btrfs/delayed-ref.h +++ b/fs/btrfs/delayed-ref.h @@ -436,6 +436,8 @@ int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info, u64 seq); void btrfs_delayed_refs_rsv_release(struct btrfs_fs_info *fs_info, int nr_refs, int nr_csums); void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans); +void btrfs_inc_delayed_refs_rsv_bg_updates(struct btrfs_fs_info *fs_info); +void btrfs_dec_delayed_refs_rsv_bg_updates(struct btrfs_fs_info *fs_info); int btrfs_delayed_refs_rsv_refill(struct btrfs_fs_info *fs_info, enum btrfs_reserve_flush_enum flush); void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info, diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index a970da7263b3..178312c2efc8 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -4774,7 +4774,7 @@ void btrfs_cleanup_dirty_bgs(struct btrfs_transaction *cur_trans, spin_unlock(&cur_trans->dirty_bgs_lock); btrfs_put_block_group(cache); - btrfs_delayed_refs_rsv_release(fs_info, 1, 0); + btrfs_dec_delayed_refs_rsv_bg_updates(fs_info); spin_lock(&cur_trans->dirty_bgs_lock); } spin_unlock(&cur_trans->dirty_bgs_lock); -- cgit v1.2.3