[PATCH v2 15/15] btrfs: add tracepoints for extent map shrinker events

[fdmanana@kernel.org]

From: Filipe Manana <fdmanana@suse.com>

Add some tracepoints for the extent map shrinker to help debug and analyse
main events. These have proved useful during development of the shrinker.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/extent_map.c        | 18 ++++++-
 include/trace/events/btrfs.h | 92 ++++++++++++++++++++++++++++++++++++
 2 files changed, 109 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 9791acda5b57..5c40efe39e70 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -1064,6 +1064,7 @@ static unsigned long btrfs_scan_inode(struct btrfs_inode *inode,
 			btrfs_set_inode_full_sync(inode);
 
 		remove_extent_mapping(inode, em);
+		trace_btrfs_extent_map_shrinker_remove_em(inode, em);
 		/* Drop the reference for the tree. */
 		free_extent_map(em);
 		nr_dropped++;
@@ -1118,6 +1119,12 @@ static unsigned long btrfs_extent_maps_scan(struct shrinker *shrinker,
 	unsigned long scanned = 0;
 	u64 next_root_id = 0;
 
+	if (trace_btrfs_extent_map_shrinker_scan_enter_enabled()) {
+		s64 nr = percpu_counter_sum_positive(&fs_info->evictable_extent_maps);
+
+		trace_btrfs_extent_map_shrinker_scan_enter(fs_info, sc->nr_to_scan, nr);
+	}
+
 	while (scanned < sc->nr_to_scan) {
 		struct btrfs_root *root;
 		unsigned long count;
@@ -1142,6 +1149,12 @@ static unsigned long btrfs_extent_maps_scan(struct shrinker *shrinker,
 		btrfs_put_root(root);
 	}
 
+	if (trace_btrfs_extent_map_shrinker_scan_exit_enabled()) {
+		s64 nr = percpu_counter_sum_positive(&fs_info->evictable_extent_maps);
+
+		trace_btrfs_extent_map_shrinker_scan_exit(fs_info, nr_dropped, nr);
+	}
+
 	return nr_dropped;
 }
 
@@ -1149,8 +1162,11 @@ static unsigned long btrfs_extent_maps_count(struct shrinker *shrinker,
 					     struct shrink_control *sc)
 {
 	struct btrfs_fs_info *fs_info = shrinker->private_data;
+	const s64 nr = percpu_counter_sum_positive(&fs_info->evictable_extent_maps);
+
+	trace_btrfs_extent_map_shrinker_count(fs_info, sc->nr_to_scan, nr);
 
-	return percpu_counter_sum_positive(&fs_info->evictable_extent_maps);
+	return nr;
 }
 
 int btrfs_register_extent_map_shrinker(struct btrfs_fs_info *fs_info)
diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h
index 766cfd48386c..ba49efa2bc74 100644
--- a/include/trace/events/btrfs.h
+++ b/include/trace/events/btrfs.h
@@ -2551,6 +2551,98 @@ TRACE_EVENT(btrfs_get_raid_extent_offset,
 			__entry->devid)
 );
 
+TRACE_EVENT(btrfs_extent_map_shrinker_count,
+
+	TP_PROTO(const struct btrfs_fs_info *fs_info, u64 nr_to_scan, u64 nr),
+
+	TP_ARGS(fs_info, nr_to_scan, nr),
+
+	TP_STRUCT__entry_btrfs(
+		__field(	u64,	nr_to_scan	)
+		__field(	u64,	nr		)
+	),
+
+	TP_fast_assign_btrfs(fs_info,
+		__entry->nr_to_scan	= nr_to_scan;
+		__entry->nr		= nr;
+	),
+
+	TP_printk_btrfs("nr_to_scan=%llu nr=%llu",
+			__entry->nr_to_scan, __entry->nr)
+);
+
+TRACE_EVENT(btrfs_extent_map_shrinker_scan_enter,
+
+	TP_PROTO(const struct btrfs_fs_info *fs_info, u64 nr_to_scan, u64 nr),
+
+	TP_ARGS(fs_info, nr_to_scan, nr),
+
+	TP_STRUCT__entry_btrfs(
+		__field(	u64,	nr_to_scan	)
+		__field(	u64,	nr		)
+	),
+
+	TP_fast_assign_btrfs(fs_info,
+		__entry->nr_to_scan	= nr_to_scan;
+		__entry->nr		= nr;
+	),
+
+	TP_printk_btrfs("nr_to_scan=%llu nr=%llu",
+			__entry->nr_to_scan, __entry->nr)
+);
+
+TRACE_EVENT(btrfs_extent_map_shrinker_scan_exit,
+
+	TP_PROTO(const struct btrfs_fs_info *fs_info, u64 nr_dropped, u64 nr),
+
+	TP_ARGS(fs_info, nr_dropped, nr),
+
+	TP_STRUCT__entry_btrfs(
+		__field(	u64,	nr_dropped	)
+		__field(	u64,	nr		)
+	),
+
+	TP_fast_assign_btrfs(fs_info,
+		__entry->nr_dropped	= nr_dropped;
+		__entry->nr		= nr;
+	),
+
+	TP_printk_btrfs("nr_dropped=%llu nr=%llu",
+			__entry->nr_dropped, __entry->nr)
+);
+
+TRACE_EVENT(btrfs_extent_map_shrinker_remove_em,
+
+	TP_PROTO(const struct btrfs_inode *inode, const struct extent_map *em),
+
+	TP_ARGS(inode, em),
+
+	TP_STRUCT__entry_btrfs(
+		__field(	u64,	ino		)
+		__field(	u64,	root_id		)
+		__field(	u64,	start		)
+		__field(	u64,	len		)
+		__field(	u64,	block_start	)
+		__field(	u32,	flags		)
+	),
+
+	TP_fast_assign_btrfs(inode->root->fs_info,
+		__entry->ino		= btrfs_ino(inode);
+		__entry->root_id	= inode->root->root_key.objectid;
+		__entry->start		= em->start;
+		__entry->len		= em->len;
+		__entry->block_start	= em->block_start;
+		__entry->flags		= em->flags;
+	),
+
+	TP_printk_btrfs(
+"ino=%llu root=%llu(%s) start=%llu len=%llu block_start=%llu(%s) flags=%s",
+			__entry->ino, show_root_type(__entry->root_id),
+			__entry->start, __entry->len,
+			show_map_type(__entry->block_start),
+			show_map_flags(__entry->flags))
+);
+
 #endif /* _TRACE_BTRFS_H */
 
 /* This part must be outside protection */
-- 
2.43.0