From: Chris Mason Date: Wed, 24 Sep 2008 18:51:30 +0000 (-0400) Subject: Btrfs: Raise thresholds for metadata writeback X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=24ab9cd85c11bccacbd0cce7f8e1aebd4930404c;p=deliverable%2Flinux.git Btrfs: Raise thresholds for metadata writeback Btrfs metadata writeback is fairly expensive. Once a tree block is written it must be cowed before it can be changed again. The btree writepages code has a threshold based on a count of dirty btree bytes which is updated as IO is sent out. This changes btree_writepages to skip the writeout if there are less than 32MB of dirty bytes from the btrees, improving performance across many workloads. Signed-off-by: Chris Mason --- diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index dffb8dabd533..71e81f3a765b 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -556,7 +556,7 @@ static int btree_writepages(struct address_space *mapping, if (wbc->sync_mode == WB_SYNC_NONE) { u64 num_dirty; u64 start = 0; - unsigned long thresh = 8 * 1024 * 1024; + unsigned long thresh = 32 * 1024 * 1024; if (wbc->for_kupdate) return 0; @@ -690,7 +690,7 @@ struct extent_buffer *btrfs_find_create_tree_block(struct btrfs_root *root, int btrfs_write_tree_block(struct extent_buffer *buf) { return btrfs_fdatawrite_range(buf->first_page->mapping, buf->start, - buf->start + buf->len - 1, WB_SYNC_NONE); + buf->start + buf->len - 1, WB_SYNC_ALL); } int btrfs_wait_tree_block_writeback(struct extent_buffer *buf)