From 4f4db2174d8d6cdc093cbb79d17fbfe0f4d9fbde Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Tue, 29 Sep 2015 11:40:47 -0400 Subject: [PATCH] Btrfs: keep track of max_extent_size per space_info When we are heavily fragmented we can induce a lot of latency trying to make an allocation happen that is simply not going to happen. Thankfully we keep track of our max_extent_size when going through the allocator, so if we get to the point where we are exiting find_free_extent with ENOSPC then set our space_info->max_extent_size so we can keep future allocations from having to pay this cost. We reset the max_extent_size whenever we release pinned bytes back into this space info so we can redo all the work. Thanks, Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/ctree.h | 4 ++++ fs/btrfs/extent-tree.c | 31 ++++++++++++++++++++++++++++++- 2 files changed, 34 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 16384231db82..78a8f56c7e88 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -1154,6 +1154,10 @@ struct btrfs_space_info { delalloc/allocations */ u64 bytes_readonly; /* total bytes that are read only */ + u64 max_extent_size; /* This will hold the maximum extent size of + the space info if we had an ENOSPC in the + allocator. */ + unsigned int full:1; /* indicates that we cannot allocate any more chunks for this space */ unsigned int chunk_alloc:1; /* set if we are allocating a chunk */ diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index d6b5ef4b4c72..febb5bc35a64 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3810,6 +3810,7 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags, found->bytes_readonly = 0; found->bytes_may_use = 0; found->full = 0; + found->max_extent_size = 0; found->force_alloc = CHUNK_ALLOC_NO_FORCE; found->chunk_alloc = 0; found->flush = 0; @@ -6158,6 +6159,7 @@ static int unpin_extent_range(struct btrfs_root *root, u64 start, u64 end, spin_lock(&cache->lock); cache->pinned -= len; space_info->bytes_pinned -= len; + space_info->max_extent_size = 0; percpu_counter_add(&space_info->total_bytes_pinned, -len); if (cache->ro) { space_info->bytes_readonly += len; @@ -6914,6 +6916,29 @@ static noinline int find_free_extent(struct btrfs_root *orig_root, return -ENOSPC; } + /* + * If our free space is heavily fragmented we may not be able to make + * big contiguous allocations, so instead of doing the expensive search + * for free space, simply return ENOSPC with our max_extent_size so we + * can go ahead and search for a more manageable chunk. + * + * If our max_extent_size is large enough for our allocation simply + * disable clustering since we will likely not be able to find enough + * space to create a cluster and induce latency trying. + */ + if (unlikely(space_info->max_extent_size)) { + spin_lock(&space_info->lock); + if (space_info->max_extent_size && + num_bytes > space_info->max_extent_size) { + ins->offset = space_info->max_extent_size; + spin_unlock(&space_info->lock); + return -ENOSPC; + } else if (space_info->max_extent_size) { + use_cluster = false; + } + spin_unlock(&space_info->lock); + } + /* * If the space info is for both data and metadata it means we have a * small filesystem and we can't use the clustering stuff. @@ -7287,8 +7312,12 @@ static noinline int find_free_extent(struct btrfs_root *orig_root, ret = 0; } out: - if (ret == -ENOSPC) + if (ret == -ENOSPC) { + spin_lock(&space_info->lock); + space_info->max_extent_size = max_extent_size; + spin_unlock(&space_info->lock); ins->offset = max_extent_size; + } return ret; } -- GitLab