Btfs: More metadata allocator optimizations
This lowers the empty cluster target for metadata allocations. The lower
target makes it easier to do allocations and still seems to perform well.
It also fixes the allocator loop to drop the empty cluster when things
start getting difficult, avoiding false enospc warnings.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index b8c6541..0d73a53 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2116,6 +2116,7 @@
struct btrfs_root * root = orig_root->fs_info->extent_root;
u64 total_needed = num_bytes;
u64 *last_ptr = NULL;
+ u64 last_wanted = 0;
struct btrfs_block_group_cache *block_group = NULL;
int chunk_alloc_done = 0;
int empty_cluster = 2 * 1024 * 1024;
@@ -2134,22 +2135,28 @@
if (data & BTRFS_BLOCK_GROUP_METADATA) {
last_ptr = &root->fs_info->last_alloc;
- empty_cluster = 256 * 1024;
+ empty_cluster = 64 * 1024;
}
if ((data & BTRFS_BLOCK_GROUP_DATA) && btrfs_test_opt(root, SSD))
last_ptr = &root->fs_info->last_data_alloc;
if (last_ptr) {
- if (*last_ptr)
+ if (*last_ptr) {
hint_byte = *last_ptr;
- else
+ last_wanted = *last_ptr;
+ } else
empty_size += empty_cluster;
+ } else {
+ empty_cluster = 0;
}
search_start = max(search_start, first_logical_byte(root, 0));
search_start = max(search_start, hint_byte);
total_needed += empty_size;
+ if (search_start != last_wanted)
+ last_wanted = 0;
+
block_group = btrfs_lookup_block_group(root->fs_info, search_start);
if (!block_group)
block_group = btrfs_lookup_first_block_group(root->fs_info,
@@ -2195,9 +2202,9 @@
if (search_start + num_bytes > end)
goto new_group;
- if (last_ptr && *last_ptr && search_start != *last_ptr) {
+ if (last_wanted && search_start != last_wanted) {
total_needed += empty_cluster;
- *last_ptr = 0;
+ last_wanted = 0;
/*
* if search_start is still in this block group
* then we just re-search this block group
@@ -2223,6 +2230,7 @@
if (search_start >= start &&
search_start < end) {
mutex_unlock(&block_group->alloc_mutex);
+ last_wanted = 0;
continue;
}
@@ -2240,6 +2248,11 @@
break;
}
new_group:
+ last_wanted = 0;
+ if (loop > 0) {
+ total_needed -= empty_cluster;
+ empty_cluster = 0;
+ }
mutex_unlock(&block_group->alloc_mutex);
/*
* Here's how this works.
@@ -2256,11 +2269,6 @@
if (loop == 0) {
head = &space_info->block_groups;
cur = head->next;
-
- if (last_ptr && *last_ptr) {
- total_needed += empty_cluster;
- *last_ptr = 0;
- }
loop++;
} else if (loop == 1 && cur == head) {
if (allowed_chunk_alloc && !chunk_alloc_done) {