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f616f5cd9d
linux/fs/btrfs
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Qu Wenruo f616f5cd9d btrfs: qgroup: Use delayed subtree rescan for balance 
Before this patch, qgroup code traces the whole subtree of subvolume and
reloc trees unconditionally.

This makes qgroup numbers consistent, but it could cause tons of
unnecessary extent tracing, which causes a lot of overhead.

However for subtree swap of balance, just swap both subtrees because
they contain the same contents and tree structure, so qgroup numbers
won't change.

It's the race window between subtree swap and transaction commit could
cause qgroup number change.

This patch will delay the qgroup subtree scan until COW happens for the
subtree root.

So if there is no other operations for the fs, balance won't cause extra
qgroup overhead. (best case scenario)
Depending on the workload, most of the subtree scan can still be
avoided.

Only for worst case scenario, it will fall back to old subtree swap
overhead. (scan all swapped subtrees)

[[Benchmark]]
Hardware:
	VM 4G vRAM, 8 vCPUs,
	disk is using 'unsafe' cache mode,
	backing device is SAMSUNG 850 evo SSD.
	Host has 16G ram.

Mkfs parameter:
	--nodesize 4K (To bump up tree size)

Initial subvolume contents:
	4G data copied from /usr and /lib.
	(With enough regular small files)

Snapshots:
	16 snapshots of the original subvolume.
	each snapshot has 3 random files modified.

balance parameter:
	-m

So the content should be pretty similar to a real world root fs layout.

And after file system population, there is no other activity, so it
should be the best case scenario.

                     | v4.20-rc1            | w/ patchset    | diff
-----------------------------------------------------------------------
relocated extents    | 22615                | 22457          | -0.1%
qgroup dirty extents | 163457               | 121606         | -25.6%
time (sys)           | 22.884s              | 18.842s        | -17.6%
time (real)          | 27.724s              | 22.884s        | -17.5%

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2019-02-25 14:13:26 +01:00
..
tests btrfs: remove always true if branch in find_delalloc_range 2018-12-17 14:51:44 +01:00
acl.c Btrfs: setup a nofs context for memory allocation at __btrfs_set_acl 2019-02-25 14:13:17 +01:00
async-thread.c btrfs: simplify workqueue name when allocating 2019-02-25 14:13:24 +01:00
async-thread.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
backref.c btrfs: Fix typos in comments and strings 2018-12-17 14:51:50 +01:00
backref.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
btrfs_inode.h Btrfs: fix fsync of files with multiple hard links in new directories 2018-12-17 14:51:43 +01:00
check-integrity.c btrfs: Fix typos in comments and strings 2018-12-17 14:51:50 +01:00
check-integrity.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
compression.c btrfs: Fix typos in comments and strings 2018-12-17 14:51:50 +01:00
compression.h btrfs: compression: Add linux/sizes.h for compression.h 2018-05-29 18:13:00 +02:00
ctree.c btrfs: qgroup: Use delayed subtree rescan for balance 2019-02-25 14:13:26 +01:00
ctree.h btrfs: qgroup: Introduce per-root swapped blocks infrastructure 2019-02-25 14:13:26 +01:00
dedupe.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
delayed-inode.c Btrfs: kill btrfs_clear_path_blocking 2018-10-15 17:23:38 +02:00
delayed-inode.h Btrfs: delayed-inode: use rb_first_cached for ins_root and del_root 2018-10-15 17:23:33 +02:00
delayed-ref.c btrfs: introduce delayed_refs_rsv 2018-12-17 14:51:46 +01:00
delayed-ref.h btrfs: add btrfs_delete_ref_head helper 2018-12-17 14:51:46 +01:00
dev-replace.c btrfs: merge btrfs_find_device and find_device 2019-02-25 14:13:24 +01:00
dev-replace.h btrfs: dev-replace: open code trivial locking helpers 2018-12-17 14:51:45 +01:00
dir-item.c btrfs: Remove root parameter from btrfs_insert_dir_item 2018-10-15 17:23:25 +02:00
disk-io.c btrfs: qgroup: Introduce per-root swapped blocks infrastructure 2019-02-25 14:13:26 +01:00
disk-io.h btrfs: drop extra enum initialization where using defaults 2018-12-17 14:51:43 +01:00
export.c btrfs: Remove 'objectid' member from struct btrfs_root 2018-10-15 17:23:25 +02:00
export.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
extent_io.c btrfs: Remove unused arguments from btrfs_get_extent_fiemap 2019-02-25 14:13:17 +01:00
extent_io.h btrfs: Fix typos in comments and strings 2018-12-17 14:51:50 +01:00
extent_map.c btrfs: Remove impossible condition from mergable_maps 2019-02-25 14:13:21 +01:00
extent_map.h btrfs: Remove impossible condition from mergable_maps 2019-02-25 14:13:21 +01:00
extent-tree.c btrfs: call btrfs_create_pending_block_groups unconditionally 2019-02-25 14:13:25 +01:00
file-item.c btrfs: replace btrfs_io_bio::end_io with a simple helper 2018-12-17 14:51:40 +01:00
file.c btrfs: Remove unused arguments from btrfs_get_extent_fiemap 2019-02-25 14:13:17 +01:00
free-space-cache.c Btrfs: fix deadlock on tree root leaf when finding free extent 2018-11-06 16:42:32 +01:00
free-space-cache.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
free-space-tree.c btrfs: use EXPORT_FOR_TESTS for conditionally exported functions 2018-12-17 14:51:37 +01:00
free-space-tree.h btrfs: Remove fs_info argument from add_to_free_space_tree 2018-05-28 18:07:36 +02:00
inode-item.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
inode-map.c btrfs: prune unused includes 2018-08-06 13:12:43 +02:00
inode-map.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
inode.c btrfs: Remove not_found_em label from btrfs_get_extent 2019-02-25 14:13:22 +01:00
ioctl.c btrfs: merge btrfs_find_device and find_device 2019-02-25 14:13:24 +01:00
Kconfig btrfs: add SPDX header to Kconfig 2018-04-12 16:29:55 +02:00
locking.c btrfs: replace waitqueue_actvie with cond_wake_up 2018-05-28 18:23:09 +02:00
locking.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
lzo.c btrfs: Fix typos in comments and strings 2018-12-17 14:51:50 +01:00
Makefile btrfs: Remove custom crc32c init code 2018-03-26 15:09:39 +02:00
math.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
ordered-data.c Btrfs: remove no longer used stuff for tracking pending ordered extents 2018-12-17 14:51:25 +01:00
ordered-data.h btrfs: switch BTRFS_ORDERED_* to enums 2018-12-17 14:51:43 +01:00
orphan.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
print-tree.c btrfs: annotate unlikely branches after V0 extent type removal 2018-08-06 13:12:41 +02:00
print-tree.h btrfs: print-tree: debugging output enhancement 2018-04-20 19:18:16 +02:00
props.c btrfs: property: Set incompat flag if lzo/zstd compression is set 2018-05-17 14:18:25 +02:00
props.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
qgroup.c btrfs: qgroup: Use delayed subtree rescan for balance 2019-02-25 14:13:26 +01:00
qgroup.h btrfs: qgroup: Use delayed subtree rescan for balance 2019-02-25 14:13:26 +01:00
raid56.c btrfs: Fix typos in comments and strings 2018-12-17 14:51:50 +01:00
raid56.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
rcu-string.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
reada.c btrfs: dev-replace: open code trivial locking helpers 2018-12-17 14:51:45 +01:00
ref-verify.c btrfs: Fix typos in comments and strings 2018-12-17 14:51:50 +01:00
ref-verify.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
relocation.c btrfs: qgroup: Use delayed subtree rescan for balance 2019-02-25 14:13:26 +01:00
root-tree.c btrfs: Remove fs_info from btrfs_add_root_ref 2018-08-06 13:13:00 +02:00
scrub.c btrfs: scrub: print messages when started or finished 2019-02-25 14:13:24 +01:00
send.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
send.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
struct-funcs.c btrfs: prune unused includes 2018-08-06 13:12:43 +02:00
super.c for-5.0-rc4-tag 2019-02-03 08:48:33 -08:00
sysfs.c btrfs: Add sysfs support for metadata_uuid feature 2018-12-17 14:51:37 +01:00
sysfs.h btrfs: drop extra enum initialization where using defaults 2018-12-17 14:51:43 +01:00
transaction.c btrfs: qgroup: Introduce per-root swapped blocks infrastructure 2019-02-25 14:13:26 +01:00
transaction.h btrfs: drop extra enum initialization where using defaults 2018-12-17 14:51:43 +01:00
tree-checker.c btrfs: Fix typos in comments and strings 2018-12-17 14:51:50 +01:00
tree-checker.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
tree-defrag.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
tree-log.c btrfs: Fix typos in comments and strings 2018-12-17 14:51:50 +01:00
tree-log.h Btrfs: remove no longer used io_err from btrfs_log_ctx 2018-12-17 14:51:31 +01:00
ulist.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
ulist.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
uuid-tree.c btrfs: Remove fs_info argument from btrfs_uuid_tree_rem 2018-05-30 16:46:53 +02:00
volumes.c btrfs: merge btrfs_find_device and find_device 2019-02-25 14:13:24 +01:00
volumes.h btrfs: merge btrfs_find_device and find_device 2019-02-25 14:13:24 +01:00
xattr.c Btrfs: use nofs context when initializing security xattrs to avoid deadlock 2018-12-17 14:51:49 +01:00
xattr.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
zlib.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
zstd.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00