Josef's fs_mark test
fs_mark -d /mnt/btrfs-test -D 512 -t 16 -n 4096 -F -S0
on a 2GB single metadata fs leaves about 400Mb of metadata almost unused.
This patch reduces metadata chunk allocations by considering the proper
metadata chunk size of 200MB in should_alloc_chunk(), not the default 256MB
which is set in __btrfs_alloc_chunk().
Signed-off-by: Itaru Kitayama <kitayama@xxxxxxxxxxxx>
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 8c26441..54ab490 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3241,6 +3241,8 @@ static int should_alloc_chunk(struct btrfs_root *root,
struct btrfs_space_info *sinfo, u64 alloc_bytes)
{
u64 num_bytes = sinfo->total_bytes - sinfo->bytes_readonly;
+ u64 total_rw_bytes = root->fs_info->fs_devices->total_rw_bytes;
+ u64 max_chunk_size;
u64 thresh;
if (sinfo->bytes_used + sinfo->bytes_reserved +
@@ -3251,8 +3253,9 @@ static int should_alloc_chunk(struct btrfs_root *root,
alloc_bytes < div_factor(num_bytes, 8))
return 0;
+ max_chunk_size = min(256 * 1024 * 1024, div_factor(total_rw_bytes, 1));
thresh = btrfs_super_total_bytes(&root->fs_info->super_copy);
- thresh = max_t(u64, 256 * 1024 * 1024, div_factor_fine(thresh, 5));
+ thresh = max_t(u64, max_chunk_size, div_factor_fine(thresh, 5));
if (num_bytes > thresh && sinfo->bytes_used < div_factor(num_bytes, 3))
return 0;
--
Itaru Kitayama <kitayama@xxxxxxxxxxxx>
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