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: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 78 insertions, 3 deletions

diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h
index 8a422e29d064..cc2eaab28d58 100644
--- a/include/trace/events/btrfs.h
+++ b/include/trace/events/btrfs.h
@@ -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,