From 32cb0840ce8e13901fe71a9a8e834a531802ffc4 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Fri, 18 Mar 2011 16:16:21 -0400 Subject: [PATCH] Btrfs: don't be as aggressive about using bitmaps We have been creating bitmaps for small extents unconditionally forever. This was great when testing to make sure the bitmap stuff was working, but is overkill normally. So instead of always adding small chunks of free space to bitmaps, only start doing it if we go past half of our extent threshold. This will keeps us from creating a bitmap for just one small free extent at the front of the block group, and will make the allocator a little faster as a result. Thanks, Signed-off-by: Josef Bacik --- fs/btrfs/free-space-cache.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index 63776ae72f9e..4ab35ea0443f 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -1287,9 +1287,22 @@ static int insert_into_bitmap(struct btrfs_block_group_cache *block_group, * If we are below the extents threshold then we can add this as an * extent, and don't have to deal with the bitmap */ - if (block_group->free_extents < block_group->extents_thresh && - info->bytes > block_group->sectorsize * 4) - return 0; + if (block_group->free_extents < block_group->extents_thresh) { + /* + * If this block group has some small extents we don't want to + * use up all of our free slots in the cache with them, we want + * to reserve them to larger extents, however if we have plent + * of cache left then go ahead an dadd them, no sense in adding + * the overhead of a bitmap if we don't have to. + */ + if (info->bytes <= block_group->sectorsize * 4) { + if (block_group->free_extents * 2 <= + block_group->extents_thresh) + return 0; + } else { + return 0; + } + } /* * some block groups are so tiny they can't be enveloped by a bitmap, so