btrfs: qgroup: Move half of the qgroup accounting time out of commit trans
Just as Filipe pointed out, the most time consuming parts of qgroup are
btrfs_qgroup_account_extents() and
btrfs_qgroup_prepare_account_extents().
Which both call btrfs_find_all_roots() to get old_roots and new_roots
ulist.
What makes things worse is, we're calling that expensive
btrfs_find_all_roots() at transaction committing time with
TRANS_STATE_COMMIT_DOING, which will blocks all incoming transaction.
Such behavior is necessary for @new_roots search as current
btrfs_find_all_roots() can't do it correctly so we do call it just
before switch commit roots.
However for @old_roots search, it's not necessary as such search is
based on commit_root, so it will always be correct and we can move it
out of transaction committing.
This patch moves the @old_roots search part out of
commit_transaction(), so in theory we can half the time qgroup time
consumption at commit_transaction().
But please note that, this won't speedup qgroup overall, the total time
consumption is still the same, just reduce the performance stall.
Cc: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index a48bf54..a5da750 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1464,8 +1464,9 @@ int btrfs_qgroup_prepare_account_extents(struct btrfs_trans_handle *trans,
while (node) {
record = rb_entry(node, struct btrfs_qgroup_extent_record,
node);
- ret = btrfs_find_all_roots(NULL, fs_info, record->bytenr, 0,
- &record->old_roots);
+ if (WARN_ON(!record->old_roots))
+ ret = btrfs_find_all_roots(NULL, fs_info,
+ record->bytenr, 0, &record->old_roots);
if (ret < 0)
break;
if (qgroup_to_skip)
@@ -1504,6 +1505,28 @@ int btrfs_qgroup_trace_extent_nolock(struct btrfs_fs_info *fs_info,
return 0;
}
+int btrfs_qgroup_trace_extent_post(struct btrfs_fs_info *fs_info,
+ struct btrfs_qgroup_extent_record *qrecord)
+{
+ struct ulist *old_root;
+ u64 bytenr = qrecord->bytenr;
+ int ret;
+
+ ret = btrfs_find_all_roots(NULL, fs_info, bytenr, 0, &old_root);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * Here we don't need to get the lock of
+ * trans->transaction->delayed_refs, since inserted qrecord won't
+ * be deleted, only qrecord->node may be modified (new qrecord insert)
+ *
+ * So modifying qrecord->old_roots is safe here
+ */
+ qrecord->old_roots = old_root;
+ return 0;
+}
+
int btrfs_qgroup_trace_extent(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytenr, u64 num_bytes,
gfp_t gfp_flag)
@@ -1529,9 +1552,11 @@ int btrfs_qgroup_trace_extent(struct btrfs_trans_handle *trans,
spin_lock(&delayed_refs->lock);
ret = btrfs_qgroup_trace_extent_nolock(fs_info, delayed_refs, record);
spin_unlock(&delayed_refs->lock);
- if (ret > 0)
+ if (ret > 0) {
kfree(record);
- return 0;
+ return 0;
+ }
+ return btrfs_qgroup_trace_extent_post(fs_info, record);
}
int btrfs_qgroup_trace_leaf_items(struct btrfs_trans_handle *trans,