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 <chris.mason@oracle.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index dffb8da..71e81f3 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -556,7 +556,7 @@
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 @@
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)
