Commit 854c2f36 authored by Boris Burkov's avatar Boris Burkov Committed by David Sterba
Browse files

btrfs: add more find_free_extent tracepoints 



find_free_extent is a complicated function. It consists (at least) of:

- a hint that jumps into the middle of a for loop macro
- a middle loop trying every raid level
- an outer loop ascending through ffe loop levels
- complicated logic for skipping some of those ffe loop levels
- multiple underlying in-bg allocators (zoned, cluster, no cluster)

Which is all to say that more tracing is helpful for debugging its
behavior. Add two new tracepoints: at the entrance to the block_groups
loop (hit for every raid level and every ffe_ctl loop) and at the point
we seriously consider a block_group for allocation. This way we can see
the whole path through the algorithm, including hints, multiple loops,
etc.

Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarBoris Burkov <boris@bur.io>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent cfc2de0f

fs/btrfs/extent-tree.c

+4 −0
Original line number Diff line number Diff line
@@ -4261,6 +4261,7 @@ static noinline int find_free_extent(struct btrfs_root *root, 
							block_group->flags);

				btrfs_lock_block_group(block_group,

						       ffe_ctl->delalloc);

				ffe_ctl->hinted = true;

				goto have_block_group;

			}

		} else if (block_group) {
@@ -4268,6 +4269,7 @@ static noinline int find_free_extent(struct btrfs_root *root, 
		}

	}

search:

	trace_find_free_extent_search_loop(root, ffe_ctl);

	ffe_ctl->have_caching_bg = false;

	if (ffe_ctl->index == btrfs_bg_flags_to_raid_index(ffe_ctl->flags) ||

	    ffe_ctl->index == 0)
@@ -4277,6 +4279,7 @@ static noinline int find_free_extent(struct btrfs_root *root, 
			    &space_info->block_groups[ffe_ctl->index], list) {

		struct btrfs_block_group *bg_ret;



		ffe_ctl->hinted = false;

		/* If the block group is read-only, we can skip it entirely. */

		if (unlikely(block_group->ro)) {

			if (ffe_ctl->for_treelog)
@@ -4318,6 +4321,7 @@ static noinline int find_free_extent(struct btrfs_root *root, 
		}



have_block_group:

		trace_find_free_extent_have_block_group(root, ffe_ctl, block_group);

		ffe_ctl->cached = btrfs_block_group_done(block_group);

		if (unlikely(!ffe_ctl->cached)) {

			ffe_ctl->have_caching_bg = true;

fs/btrfs/extent-tree.h

+3 −0
Original line number Diff line number Diff line
@@ -76,6 +76,9 @@ struct find_free_extent_ctl { 


	/* Allocation policy */

	enum btrfs_extent_allocation_policy policy;



	/* Whether or not the allocator is currently following a hint */

	bool hinted;

};



enum btrfs_inline_ref_type {

include/trace/events/btrfs.h

+78 −3
Original line number Diff line number Diff line
@@ -1268,6 +1268,77 @@ TRACE_EVENT(find_free_extent, 
				 BTRFS_GROUP_FLAGS))

);



TRACE_EVENT(find_free_extent_search_loop,



	TP_PROTO(const struct btrfs_root *root,

		 const struct find_free_extent_ctl *ffe_ctl),



	TP_ARGS(root, ffe_ctl),



	TP_STRUCT__entry_btrfs(

		__field(	u64,	root_objectid		)

		__field(	u64,	num_bytes		)

		__field(	u64,	empty_size		)

		__field(	u64,	flags			)

		__field(	u64,	loop			)

	),



	TP_fast_assign_btrfs(root->fs_info,

		__entry->root_objectid	= root->root_key.objectid;

		__entry->num_bytes	= ffe_ctl->num_bytes;

		__entry->empty_size	= ffe_ctl->empty_size;

		__entry->flags		= ffe_ctl->flags;

		__entry->loop		= ffe_ctl->loop;

	),



	TP_printk_btrfs("root=%llu(%s) len=%llu empty_size=%llu flags=%llu(%s) loop=%llu",

		  show_root_type(__entry->root_objectid),

		  __entry->num_bytes, __entry->empty_size, __entry->flags,

		  __print_flags((unsigned long)__entry->flags, "|", BTRFS_GROUP_FLAGS),

		  __entry->loop)

);



TRACE_EVENT(find_free_extent_have_block_group,



	TP_PROTO(const struct btrfs_root *root,

		 const struct find_free_extent_ctl *ffe_ctl,

		 const struct btrfs_block_group *block_group),



	TP_ARGS(root, ffe_ctl, block_group),



	TP_STRUCT__entry_btrfs(

		__field(	u64,	root_objectid		)

		__field(	u64,	num_bytes		)

		__field(	u64,	empty_size		)

		__field(	u64,	flags			)

		__field(	u64,	loop			)

		__field(	bool,	hinted			)

		__field(	u64,	bg_start		)

		__field(	u64,	bg_flags		)

	),



	TP_fast_assign_btrfs(root->fs_info,

		__entry->root_objectid	= root->root_key.objectid;

		__entry->num_bytes	= ffe_ctl->num_bytes;

		__entry->empty_size	= ffe_ctl->empty_size;

		__entry->flags		= ffe_ctl->flags;

		__entry->loop		= ffe_ctl->loop;

		__entry->hinted		= ffe_ctl->hinted;

		__entry->bg_start	= block_group->start;

		__entry->bg_flags	= block_group->flags;

	),



	TP_printk_btrfs(

"root=%llu(%s) len=%llu empty_size=%llu flags=%llu(%s) loop=%llu hinted=%d block_group=%llu bg_flags=%llu(%s)",

		  show_root_type(__entry->root_objectid),

		  __entry->num_bytes, __entry->empty_size, __entry->flags,

		  __print_flags((unsigned long)__entry->flags, "|", BTRFS_GROUP_FLAGS),

		  __entry->loop, __entry->hinted,

		  __entry->bg_start, __entry->bg_flags,

		  __print_flags((unsigned long)__entry->bg_flags, "|",

				 BTRFS_GROUP_FLAGS))

);



DECLARE_EVENT_CLASS(btrfs__reserve_extent,



	TP_PROTO(const struct btrfs_block_group *block_group,
@@ -1280,6 +1351,8 @@ DECLARE_EVENT_CLASS(btrfs__reserve_extent, 
		__field(	u64,	flags			)

		__field(	u64,	start			)

		__field(	u64,	len			)

		__field(	u64,	loop			)

		__field(	bool,	hinted			)

	),



	TP_fast_assign_btrfs(block_group->fs_info,
@@ -1287,15 +1360,17 @@ DECLARE_EVENT_CLASS(btrfs__reserve_extent, 
		__entry->flags		= block_group->flags;

		__entry->start		= ffe_ctl->search_start;

		__entry->len		= ffe_ctl->num_bytes;

		__entry->loop		= ffe_ctl->loop;

		__entry->hinted		= ffe_ctl->hinted;

	),



	TP_printk_btrfs("root=%llu(%s) block_group=%llu flags=%llu(%s) "

		  "start=%llu len=%llu",

	TP_printk_btrfs(

"root=%llu(%s) block_group=%llu flags=%llu(%s) start=%llu len=%llu loop=%llu hinted=%d",

		  show_root_type(BTRFS_EXTENT_TREE_OBJECTID),

		  __entry->bg_objectid,

		  __entry->flags, __print_flags((unsigned long)__entry->flags,

						"|", BTRFS_GROUP_FLAGS),

		  __entry->start, __entry->len)

		  __entry->start, __entry->len, __entry->loop, __entry->hinted)

);



DEFINE_EVENT(btrfs__reserve_extent, btrfs_reserve_extent,