From: Michael Anthony Knyszek <mknyszek@google.com>
Date: Mon, 11 Feb 2019 17:20:59 +0000 (+0000)
Subject: runtime: use iterator instead of raw node for treap find
X-Git-Tag: go1.13beta1~766
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=7bb8fc10331eacc34bd38dc557a3856c8923c605;p=gostls13.git

runtime: use iterator instead of raw node for treap find

Right now the mTreap structure exposes the treapNode structure through
only one interface: find. There's no reason (performance or otherwise)
for exposing this, and we get a cleaner abstraction through the
iterators this way. This change also makes it easier to make changes to
the mTreap implementation without violating its interface.

Change-Id: I5ef86b8ac81a47d05d8404df65af9ec5f419dc40
Reviewed-on: https://go-review.googlesource.com/c/go/+/164098
Reviewed-by: Austin Clements <austin@google.com>
---

diff --git a/src/runtime/mgclarge.go b/src/runtime/mgclarge.go
index 7b01a11780..dba617c25d 100644
--- a/src/runtime/mgclarge.go
+++ b/src/runtime/mgclarge.go
@@ -295,13 +295,13 @@ func (root *mTreap) removeNode(t *treapNode) {
 	mheap_.treapalloc.free(unsafe.Pointer(t))
 }
 
-// find searches for, finds, and returns the treap node containing the
-// smallest span that can hold npages. If no span has at least npages
-// it returns nil.
+// find searches for, finds, and returns the treap iterator representing
+// the position of the smallest span that can hold npages. If no span has
+// at least npages it returns an invalid iterator.
 // This is slightly more complicated than a simple binary tree search
 // since if an exact match is not found the next larger node is
 // returned.
-func (root *mTreap) find(npages uintptr) *treapNode {
+func (root *mTreap) find(npages uintptr) treapIter {
 	t := root.treap
 	for t != nil {
 		if t.spanKey == nil {
@@ -312,10 +312,10 @@ func (root *mTreap) find(npages uintptr) *treapNode {
 		} else if t.left != nil && t.left.npagesKey >= npages {
 			t = t.left
 		} else {
-			return t
+			return treapIter{t}
 		}
 	}
-	return nil
+	return treapIter{}
 }
 
 // removeSpan searches for, finds, deletes span along with
diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index 8b7ed742c9..e9cd62d7d8 100644
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -1126,12 +1126,12 @@ func (h *mheap) pickFreeSpan(npage uintptr) *mspan {
 	// Note that we want the _smaller_ free span, i.e. the free span
 	// closer in size to the amount we requested (npage).
 	var s *mspan
-	if tf != nil && (ts == nil || tf.spanKey.npages <= ts.spanKey.npages) {
-		s = tf.spanKey
-		h.free.removeNode(tf)
-	} else if ts != nil && (tf == nil || tf.spanKey.npages > ts.spanKey.npages) {
-		s = ts.spanKey
-		h.scav.removeNode(ts)
+	if tf.valid() && (!ts.valid() || tf.span().npages <= ts.span().npages) {
+		s = tf.span()
+		h.free.erase(tf)
+	} else if ts.valid() && (!tf.valid() || tf.span().npages > ts.span().npages) {
+		s = ts.span()
+		h.scav.erase(ts)
 	}
 	return s
 }