btrfs: qgroup: Introduce trace event to analyse the number of dirty extents accounted

Number of qgroup dirty extents is directly linked to the performance
overhead, so add a new trace event, trace_qgroup_num_dirty_extents(), to
record how many dirty extents is processed in
btrfs_qgroup_account_extents().

This will be pretty handy to analyze later balance performance
improvement.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

2 files changed, 25 insertions, 0 deletions

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index bdd8c0da6e32..8a03adc11f53 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2132,6 +2132,7 @@ int btrfs_qgroup_account_extents(struct btrfs_trans_handle *trans)
         struct btrfs_delayed_ref_root *delayed_refs;
         struct ulist *new_roots = NULL;
         struct rb_node *node;
+        u64 num_dirty_extents = 0;
         u64 qgroup_to_skip;
         int ret = 0;
 
@@ -2141,6 +2142,7 @@ int btrfs_qgroup_account_extents(struct btrfs_trans_handle *trans)
                 record = rb_entry(node, struct btrfs_qgroup_extent_record,
                                   node);
 
+                num_dirty_extents++;
                 trace_btrfs_qgroup_account_extents(fs_info, record);
 
                 if (!ret) {
@@ -2186,6 +2188,8 @@ cleanup:
                 kfree(record);
 
         }
+        trace_qgroup_num_dirty_extents(fs_info, trans->transid,
+                                       num_dirty_extents);
         return ret;
 }
 
diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h
index abe3ff774f58..8568946f491d 100644
--- a/include/trace/events/btrfs.h
+++ b/include/trace/events/btrfs.h
@@ -1576,6 +1576,27 @@ DEFINE_EVENT(btrfs_qgroup_extent, btrfs_qgroup_trace_extent,
         TP_ARGS(fs_info, rec)
 );
 
+TRACE_EVENT(qgroup_num_dirty_extents,
+
+        TP_PROTO(const struct btrfs_fs_info *fs_info, u64 transid,
+                 u64 num_dirty_extents),
+
+        TP_ARGS(fs_info, transid, num_dirty_extents),
+
+        TP_STRUCT__entry_btrfs(
+                __field(        u64, transid                    )
+                __field(        u64, num_dirty_extents          )
+        ),
+
+        TP_fast_assign_btrfs(fs_info,
+                __entry->transid           = transid;
+                __entry->num_dirty_extents = num_dirty_extents;
+        ),
+
+        TP_printk_btrfs("transid=%llu num_dirty_extents=%llu",
+                __entry->transid, __entry->num_dirty_extents)
+);
+
 TRACE_EVENT(btrfs_qgroup_account_extent,
 
         TP_PROTO(const struct btrfs_fs_info *fs_info, u64 transid, u64 bytenr,