From: Andre Noll <maan@tuebingen.mpg.de>
Date: Fri, 30 Dec 2022 13:09:06 +0000 (+0100)
Subject: btr: Speed up btr_node_status().
X-Git-Url: http://git.tue.mpg.de/?a=commitdiff_plain;h=db654ceb7ced70cdd133c547196b3de4207e3112;p=paraslash.git

btr: Speed up btr_node_status().

Currently we sum up the sizes of all buffers in the input queue just to
determine if the total size exceeds a small threshold. That's silly
and expensive if there are many buffers. Fix that by introducing
a helper which breaks out of the loop as soon as know the answer
because the threshold is exceeded.

User time: 150s -> 147s, speedup: 2%
---

diff --git a/buffer_tree.c b/buffer_tree.c
index 35353f56..5d97f86f 100644
--- a/buffer_tree.c
+++ b/buffer_tree.c
@@ -833,6 +833,22 @@ size_t btr_get_input_queue_size(struct btr_node *btrn)
 	return size;
 }
 
+static bool min_iqs_available(size_t min_iqs, struct btr_node *btrn)
+{
+	struct btr_buffer_reference *br;
+	size_t have = 0, wrap_consumed = 0;
+
+	FOR_EACH_BUFFER_REF(br, btrn) {
+		if (br->wrap_count != 0) {
+			wrap_consumed = br->consumed;
+			continue;
+		}
+		have += br_available_bytes(br);
+		if (have > wrap_consumed + min_iqs)
+			return true;
+	}
+	return false;
+}
 /**
  * Remove a node from the buffer tree, reconnecting parent and children.
  *
@@ -1202,9 +1218,6 @@ struct btr_node *btr_search_node(const char *name, struct btr_node *root)
 int btr_node_status(struct btr_node *btrn, size_t min_iqs,
 	enum btr_node_type type)
 {
-	size_t iqs;
-
-	assert(btrn);
 	if (type != BTR_NT_LEAF && btr_no_children(btrn))
 		return -E_BTR_NO_CHILD;
 	if (type != BTR_NT_ROOT && btr_eof(btrn))
@@ -1214,12 +1227,9 @@ int btr_node_status(struct btr_node *btrn, size_t min_iqs,
 		return 0;
 	if (type == BTR_NT_ROOT)
 		return 1;
-	iqs = btr_get_input_queue_size(btrn);
-	if (iqs == 0) /* we have a parent, because not eof */
-		return 0;
-	if (iqs < min_iqs && !btr_no_parent(btrn))
-		return 0;
-	return 1;
+	if (min_iqs_available(min_iqs, btrn))
+		return 1;
+	return btr_no_parent(btrn);
 }
 
 /**