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Btrfs: Raise thresholds for metadata writeback

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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>
This commit is contained in:
Chris Mason 2008-09-24 14:51:30 -04:00
parent 4434c33c7f
commit 24ab9cd85c
1 changed files with 2 additions and 2 deletions
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4
fs/btrfs/disk-io.c
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@ -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)