linux/fs/btrfs
Filipe Manana ace75066ce btrfs: improve btree readahead for full send operations
Currently a full send operation uses the standard btree readahead when
iterating over the subvolume/snapshot btree, which despite bringing good
performance benefits, it could be improved in a few aspects for use cases
such as full send operations, which are guaranteed to visit every node
and leaf of a btree, in ascending and sequential order. The limitations
of that standard btree readahead implementation are the following:

1) It only triggers readahead for leaves that are physically close
   to the leaf being read, within a 64K range;

2) It only triggers readahead for the next or previous leaves if the
   leaf being read is not currently in memory;

3) It never triggers readahead for nodes.

So add a new readahead mode that addresses all these points and use it
for full send operations.

The following test script was used to measure the improvement on a box
using an average, consumer grade, spinning disk and with 16GiB of RAM:

  $ cat test.sh
  #!/bin/bash

  DEV=/dev/sdj
  MNT=/mnt/sdj
  MKFS_OPTIONS="--nodesize 16384"     # default, just to be explicit
  MOUNT_OPTIONS="-o max_inline=2048"  # default, just to be explicit

  mkfs.btrfs -f $MKFS_OPTIONS $DEV > /dev/null
  mount $MOUNT_OPTIONS $DEV $MNT

  # Create files with inline data to make it easier and faster to create
  # large btrees.
  add_files()
  {
      local total=$1
      local start_offset=$2
      local number_jobs=$3
      local total_per_job=$(($total / $number_jobs))

      echo "Creating $total new files using $number_jobs jobs"
      for ((n = 0; n < $number_jobs; n++)); do
          (
              local start_num=$(($start_offset + $n * $total_per_job))
              for ((i = 1; i <= $total_per_job; i++)); do
                  local file_num=$((start_num + $i))
                  local file_path="$MNT/file_${file_num}"
                  xfs_io -f -c "pwrite -S 0xab 0 2000" $file_path > /dev/null
                  if [ $? -ne 0 ]; then
                      echo "Failed creating file $file_path"
                      break
                  fi
              done
          ) &
          worker_pids[$n]=$!
      done

      wait ${worker_pids[@]}

      sync
      echo
      echo "btree node/leaf count: $(btrfs inspect-internal dump-tree -t 5 $DEV | egrep '^(node|leaf) ' | wc -l)"
  }

  initial_file_count=500000
  add_files $initial_file_count 0 4

  echo
  echo "Creating first snapshot..."
  btrfs subvolume snapshot -r $MNT $MNT/snap1

  echo
  echo "Adding more files..."
  add_files $((initial_file_count / 4)) $initial_file_count 4

  echo
  echo "Updating 1/50th of the initial files..."
  for ((i = 1; i < $initial_file_count; i += 50)); do
      xfs_io -c "pwrite -S 0xcd 0 20" $MNT/file_$i > /dev/null
  done

  echo
  echo "Creating second snapshot..."
  btrfs subvolume snapshot -r $MNT $MNT/snap2

  umount $MNT

  echo 3 > /proc/sys/vm/drop_caches
  blockdev --flushbufs $DEV &> /dev/null
  hdparm -F $DEV &> /dev/null

  mount $MOUNT_OPTIONS $DEV $MNT

  echo
  echo "Testing full send..."
  start=$(date +%s)
  btrfs send $MNT/snap1 > /dev/null
  end=$(date +%s)
  echo
  echo "Full send took $((end - start)) seconds"

  umount $MNT

The durations of the full send operation in seconds were the following:

Before this change:  217 seconds
After this change:   205 seconds (-5.7%)

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-04-19 17:25:17 +02:00
..
tests idmapped-mounts-v5.12 2021-02-23 13:39:45 -08:00
acl.c fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
async-thread.c Btrfs: fix crash during unmount due to race with delayed inode workers 2020-03-23 17:01:51 +01:00
async-thread.h Btrfs: fix crash during unmount due to race with delayed inode workers 2020-03-23 17:01:51 +01:00
backref.c btrfs: move the tree mod log code into its own file 2021-04-19 17:25:16 +02:00
backref.h btrfs: add asserts for deleting backref cache nodes 2021-02-08 22:58:56 +01:00
block-group.c btrfs: fix exhaustion of the system chunk array due to concurrent allocations 2021-04-19 17:25:17 +02:00
block-group.h btrfs: fix race between writes to swap files and scrub 2021-02-22 18:07:15 +01:00
block-rsv.c btrfs: introduce mount option rescue=ignorebadroots 2020-12-08 15:53:41 +01:00
block-rsv.h btrfs: Remove __ prefix from btrfs_block_rsv_release 2020-03-23 17:01:55 +01:00
btrfs_inode.h btrfs: remove stale comment and logic from btrfs_inode_in_log() 2021-04-19 17:25:16 +02:00
check-integrity.c btrfs: integrity-checker: convert block context kmap's to kmap_local_page 2021-04-19 17:25:16 +02:00
check-integrity.h btrfs: remove btrfsic_submit_bh() 2020-03-23 17:01:39 +01:00
compression.c btrfs: convert kmap to kmap_local_page, simple cases 2021-04-19 17:25:16 +02:00
compression.h btrfs: compression: move declarations to header 2020-10-07 12:06:55 +02:00
ctree.c btrfs: improve btree readahead for full send operations 2021-04-19 17:25:17 +02:00
ctree.h btrfs: improve btree readahead for full send operations 2021-04-19 17:25:17 +02:00
delalloc-space.c btrfs: fix parameter description of btrfs_inode_rsv_release/btrfs_delalloc_release_space 2021-02-08 22:58:54 +01:00
delalloc-space.h btrfs: make btrfs_delalloc_reserve_space take btrfs_inode 2020-07-27 12:55:36 +02:00
delayed-inode.c btrfs: use btrfs_inode_lock/btrfs_inode_unlock inode lock helpers 2021-04-19 17:25:15 +02:00
delayed-inode.h btrfs: make btrfs_delayed_update_inode take btrfs_inode 2020-12-08 15:54:10 +01:00
delayed-ref.c btrfs: update debug message when checking seq number of a delayed ref 2021-04-19 17:25:17 +02:00
delayed-ref.h btrfs: only let one thread pre-flush delayed refs in commit 2021-02-08 22:58:56 +01:00
dev-replace.c btrfs: do not initialize dev replace for bad dev root 2021-03-17 19:42:14 +01:00
dev-replace.h btrfs: zoned: mark block groups to copy for device-replace 2021-02-09 02:46:07 +01:00
dir-item.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
discard.c btrfs: document now parameter of peek_discard_list 2021-02-08 22:58:53 +01:00
discard.h btrfs: cleanup btrfs_discard_update_discardable usage 2020-12-08 15:54:02 +01:00
disk-io.c for-5.12-rc4-tag 2021-03-25 15:38:22 -07:00
disk-io.h btrfs: split alloc_log_tree() 2021-02-09 02:46:07 +01:00
export.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
export.h btrfs: export helpers for subvolume name/id resolution 2020-03-23 17:01:42 +01:00
extent_io.c btrfs: remove duplicated in_range() macro 2021-04-19 17:25:16 +02:00
extent_io.h btrfs: zoned: redirty released extent buffers 2021-02-09 02:46:04 +01:00
extent_map.c btrfs: fix parameter description of btrfs_add_extent_mapping 2021-02-08 22:58:53 +01:00
extent_map.h btrfs: remove extent_map::bdev 2019-11-18 23:43:44 +01:00
extent-io-tree.h btrfs: use fixed width int type for extent_state::state 2020-12-08 15:54:13 +01:00
extent-tree.c btrfs: use the new bit BTRFS_FS_TREE_MOD_LOG_USERS at btrfs_free_tree_block() 2021-04-19 17:25:16 +02:00
file-item.c btrfs: remove duplicated in_range() macro 2021-04-19 17:25:16 +02:00
file.c btrfs: fix a potential hole punching failure 2021-04-19 17:25:17 +02:00
free-space-cache.c btrfs: zoned: do not account freed region of read-only block group as zone_unusable 2021-03-04 16:16:58 +01:00
free-space-cache.h btrfs: zoned: track unusable bytes for zones 2021-02-09 02:46:03 +01:00
free-space-tree.c btrfs: fix possible free space tree corruption with online conversion 2021-01-25 18:44:37 +01:00
free-space-tree.h btrfs: rename btrfs_block_group_cache 2019-11-18 17:51:51 +01:00
inode-item.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
inode.c btrfs: update outdated comment at btrfs_orphan_cleanup() 2021-04-19 17:25:17 +02:00
ioctl.c btrfs: use btrfs_inode_lock/btrfs_inode_unlock inode lock helpers 2021-04-19 17:25:15 +02:00
Kconfig btrfs: switch to iomap for direct IO 2020-10-07 12:06:57 +02:00
locking.c btrfs: remove the recurse parameter from __btrfs_tree_read_lock 2020-12-08 15:54:09 +01:00
locking.h btrfs: remove the recurse parameter from __btrfs_tree_read_lock 2020-12-08 15:54:09 +01:00
lzo.c btrfs: convert kmap to kmap_local_page, simple cases 2021-04-19 17:25:16 +02:00
Makefile btrfs: move the tree mod log code into its own file 2021-04-19 17:25:16 +02:00
misc.h btrfs: rename tree_entry to rb_simple_node and export it 2020-05-25 11:25:19 +02:00
ordered-data.c btrfs: replace offset_in_entry with in_range 2021-04-19 17:25:14 +02:00
ordered-data.h btrfs: fix comment for btrfs ordered extent flag bits 2021-04-19 17:25:14 +02:00
orphan.c
print-tree.c btrfs: print the actual offset in btrfs_root_name 2021-01-07 17:25:05 +01:00
print-tree.h btrfs: print the actual offset in btrfs_root_name 2021-01-07 17:25:05 +01:00
props.c btrfs: simplify iget helpers 2020-05-25 11:25:37 +02:00
props.h btrfs: delete unused function btrfs_set_prop_trans 2019-04-29 19:02:54 +02:00
qgroup.c btrfs: move the tree mod log code into its own file 2021-04-19 17:25:16 +02:00
qgroup.h btrfs: export and rename qgroup_reserve_meta 2021-03-02 16:58:30 +01:00
raid56.c btrfs: raid56: convert kmaps to kmap_local_page 2021-04-19 17:25:16 +02:00
raid56.h btrfs: constify map parameter for nr_parity_stripes and nr_data_stripes 2019-07-01 13:34:58 +02:00
rcu-string.h btrfs: rcu-string: Replace zero-length array with flexible-array member 2020-03-23 17:01:53 +01:00
reada.c btrfs: subpage: make readahead work properly 2021-03-16 11:06:21 +01:00
ref-verify.c btrfs: ref-verify: use 'inline void' keyword ordering 2021-03-02 16:55:40 +01:00
ref-verify.h
reflink.c btrfs: make reflinks respect O_SYNC O_DSYNC and S_SYNC flags 2021-04-19 17:25:17 +02:00
reflink.h Btrfs: move all reflink implementation code into its own file 2020-03-23 17:01:54 +01:00
relocation.c btrfs: use btrfs_inode_lock/btrfs_inode_unlock inode lock helpers 2021-04-19 17:25:15 +02:00
root-tree.c btrfs: qgroup: fix qgroup meta rsv leak for subvolume operations 2020-10-07 12:12:13 +02:00
scrub.c btrfs: scrub: drop a few function declarations 2021-04-19 17:25:14 +02:00
send.c btrfs: improve btree readahead for full send operations 2021-04-19 17:25:17 +02:00
send.h btrfs: send: avoid copying file data 2020-10-07 12:13:17 +02:00
space-info.c btrfs: use percpu_read_positive instead of sum_positive for need_preempt 2021-04-19 17:25:17 +02:00
space-info.h btrfs: zoned: track unusable bytes for zones 2021-02-09 02:46:03 +01:00
struct-funcs.c btrfs: handle sectorsize < PAGE_SIZE case for extent buffer accessors 2020-12-09 19:16:10 +01:00
subpage.c btrfs: integrate page status update for data read path into begin/end_page_read 2021-02-08 22:59:03 +01:00
subpage.h btrfs: integrate page status update for data read path into begin/end_page_read 2021-02-08 22:59:03 +01:00
super.c btrfs: fix spurious free_space_tree remount warning 2021-03-02 16:55:55 +01:00
sysfs.c btrfs: zoned: track unusable bytes for zones 2021-02-09 02:46:03 +01:00
sysfs.h btrfs: split and refactor btrfs_sysfs_remove_devices_dir 2020-10-07 12:12:21 +02:00
transaction.c btrfs: fix exhaustion of the system chunk array due to concurrent allocations 2021-04-19 17:25:17 +02:00
transaction.h btrfs: fix exhaustion of the system chunk array due to concurrent allocations 2021-04-19 17:25:17 +02:00
tree-checker.c btrfs: tree-checker: do not error out if extent ref hash doesn't match 2021-02-22 18:07:44 +01:00
tree-checker.h
tree-defrag.c btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
tree-log.c btrfs: zoned: move log tree node allocation out of log_root_tree->log_mutex 2021-04-19 17:25:17 +02:00
tree-log.h btrfs: make fast fsyncs wait only for writeback 2020-10-07 12:06:56 +02:00
tree-mod-log.c btrfs: add and use helper to get lowest sequence number for the tree mod log 2021-04-19 17:25:17 +02:00
tree-mod-log.h btrfs: add and use helper to get lowest sequence number for the tree mod log 2021-04-19 17:25:17 +02:00
ulist.c
ulist.h
uuid-tree.c btrfs: remove unnecessary casts in printk 2020-12-08 15:53:52 +01:00
volumes.c btrfs: zoned: bail out in btrfs_alloc_chunk for bad input 2021-04-19 17:25:17 +02:00
volumes.h btrfs: zoned: relocate block group to repair IO failure in zoned filesystems 2021-02-09 02:46:07 +01:00
xattr.c for-5.12-rc1-tag 2021-03-05 12:21:14 -08:00
xattr.h
zlib.c btrfs: use memcpy_[to|from]_page() and kmap_local_page() 2021-02-26 12:45:15 +01:00
zoned.c for-5.12-rc6-tag 2021-04-11 11:53:36 -07:00
zoned.h btrfs: zoned: extend zoned allocator to use dedicated tree-log block group 2021-02-09 02:46:08 +01:00
zstd.c btrfs: use memcpy_[to|from]_page() and kmap_local_page() 2021-02-26 12:45:15 +01:00