From 4e2f84e63dc138eca91e89ccbc34f37732ce58f7 Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Mon, 27 Aug 2012 10:52:20 -0600 Subject: [PATCH] Btrfs: improve fsync by filtering extents that we want This is based on Josef's "Btrfs: turbo charge fsync". The above Josef's patch performs very good in random sync write test, because we won't have too much extents to merge. However, it does not performs good on the test: dd if=/dev/zero of=foobar bs=4k count=12500 oflag=sync The reason is when we do sequencial sync write, we need to merge the current extent just with the previous one, so that we can get accumulated extents to log: A(4k) --> AA(8k) --> AAA(12k) --> AAAA(16k) ... So we'll have to flush more and more checksum into log tree, which is the bottleneck according to my tests. But we can avoid this by telling fsync the real extents that are needed to be logged. With this, I did the above dd sync write test (size=50m), w/o (orig) w/ (josef's) w/ (this) SATA 104KB/s 109KB/s 121KB/s ramdisk 1.5MB/s 1.5MB/s 10.7MB/s (613%) Signed-off-by: Liu Bo --- fs/btrfs/extent_map.c | 20 ++++++++++++++++++++ fs/btrfs/extent_map.h | 2 ++ fs/btrfs/inode.c | 1 + fs/btrfs/tree-log.c | 6 +++--- 4 files changed, 26 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index 1fe82cfc1d9..ac606f076eb 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -203,6 +203,8 @@ static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em) em->block_start = merge->block_start; merge->in_tree = 0; if (merge->generation > em->generation) { + em->mod_start = em->start; + em->mod_len = em->len; em->generation = merge->generation; list_move(&em->list, &tree->modified_extents); } @@ -222,6 +224,7 @@ static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em) rb_erase(&merge->rb_node, &tree->map); merge->in_tree = 0; if (merge->generation > em->generation) { + em->mod_len = em->len; em->generation = merge->generation; list_move(&em->list, &tree->modified_extents); } @@ -247,6 +250,7 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len, { int ret = 0; struct extent_map *em; + bool prealloc = false; write_lock(&tree->lock); em = lookup_extent_mapping(tree, start, len); @@ -259,8 +263,21 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len, list_move(&em->list, &tree->modified_extents); em->generation = gen; clear_bit(EXTENT_FLAG_PINNED, &em->flags); + em->mod_start = em->start; + em->mod_len = em->len; + + if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) { + prealloc = true; + clear_bit(EXTENT_FLAG_PREALLOC, &em->flags); + } try_merge_map(tree, em); + + if (prealloc) { + em->mod_start = em->start; + em->mod_len = em->len; + } + free_extent_map(em); out: write_unlock(&tree->lock); @@ -298,6 +315,9 @@ int add_extent_mapping(struct extent_map_tree *tree, } atomic_inc(&em->refs); + em->mod_start = em->start; + em->mod_len = em->len; + try_merge_map(tree, em); out: return ret; diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h index 2388a60bd6e..8e6294b5135 100644 --- a/fs/btrfs/extent_map.h +++ b/fs/btrfs/extent_map.h @@ -20,6 +20,8 @@ struct extent_map { /* all of these are in bytes */ u64 start; u64 len; + u64 mod_start; + u64 mod_len; u64 orig_start; u64 block_start; u64 block_len; diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index ca4fa05171a..878116d9625 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1308,6 +1308,7 @@ out_check: em->block_start = disk_bytenr; em->bdev = root->fs_info->fs_devices->latest_bdev; set_bit(EXTENT_FLAG_PINNED, &em->flags); + set_bit(EXTENT_FLAG_PREALLOC, &em->flags); while (1) { write_lock(&em_tree->lock); ret = add_extent_mapping(em_tree, em); diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 58075d711d2..71e71539ffb 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -2833,8 +2833,8 @@ static int log_one_extent(struct btrfs_trans_handle *trans, struct btrfs_root *log = root->log_root; struct btrfs_file_extent_item *fi; struct btrfs_key key; - u64 start = em->start; - u64 len = em->len; + u64 start = em->mod_start; + u64 len = em->mod_len; u64 num_bytes; int nritems; int ret; @@ -2970,7 +2970,7 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans, * sequential then we need to copy the items we have and redo * our search */ - if (args.nr && em->start != args.next_offset) { + if (args.nr && em->mod_start != args.next_offset) { ret = copy_items(trans, log, dst_path, args.src, args.start_slot, args.nr, LOG_INODE_ALL); -- 2.20.1