Btrfs: Improve metadata read latencies
This fixes latency problems on metadata reads by making sure they
don't go through the async submit queue, and by tuning down the amount
of readahead done during btree searches.
Also, the btrfs bdi congestion function is tuned to ignore the
number of pending async bios and checksums pending. There is additional
code that throttles new async bios now and the congestion function
doesn't need to worry about it anymore.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index f82f8db..ac61c50 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1285,16 +1285,16 @@
}
search = btrfs_node_blockptr(node, nr);
if ((search >= lowest_read && search <= highest_read) ||
- (search < lowest_read && lowest_read - search <= 32768) ||
- (search > highest_read && search - highest_read <= 32768)) {
+ (search < lowest_read && lowest_read - search <= 16384) ||
+ (search > highest_read && search - highest_read <= 16384)) {
readahead_tree_block(root, search, blocksize,
btrfs_node_ptr_generation(node, nr));
nread += blocksize;
}
nscan++;
- if (path->reada < 2 && (nread > (256 * 1024) || nscan > 32))
+ if (path->reada < 2 && (nread > (64 * 1024) || nscan > 32))
break;
- if(nread > (1024 * 1024) || nscan > 128)
+ if(nread > (256 * 1024) || nscan > 128)
break;
if (search < lowest_read)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 1bb54d6..3b0e974 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -605,7 +605,7 @@
BUG_ON(ret);
return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
- mirror_num, 1);
+ mirror_num, 0);
}
return btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
inode, rw, bio, mirror_num, 0,
@@ -1139,11 +1139,11 @@
struct list_head *cur;
struct btrfs_device *device;
struct backing_dev_info *bdi;
-
+#if 0
if ((bdi_bits & (1 << BDI_write_congested)) &&
btrfs_congested_async(info, 0))
return 1;
-
+#endif
list_for_each(cur, &info->fs_devices->devices) {
device = list_entry(cur, struct btrfs_device, dev_list);
if (!device->bdev)