From b7216e783d7113a58e9e2eea9fec665aad28e23f Mon Sep 17 00:00:00 2001
From: Johannes Kimmel <fff@bareminimum.eu>
Date: Mon, 13 Nov 2023 23:50:26 +0100
Subject: [PATCH] correctly precalculate the minimum free prefix length on
 alloc, so recalculation can be skipped for deeply nested inserts

---
 ipalloc/ipalloc.go | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/ipalloc/ipalloc.go b/ipalloc/ipalloc.go
index 69860d1..e7ab035 100644
--- a/ipalloc/ipalloc.go
+++ b/ipalloc/ipalloc.go
@@ -112,12 +112,14 @@ func (t *tree) Alloc(bits int) *tree {
 		return nil
 	}
 
+	tofix := best
+
 	// the first insert can be into a new hi branch
 	if best.lo != nil {
 		best.hi = &tree{
 			prefix:     SplitPrefixHi(best.prefix),
 			parent:     best,
-			minfreelen: best.prefix.Bits() + 1,
+			minfreelen: best.prefix.Bits() + 2,
 		}
 		best = best.hi
 	}
@@ -127,12 +129,14 @@ func (t *tree) Alloc(bits int) *tree {
 		best.lo = &tree{
 			prefix:     SplitPrefixLo(best.prefix),
 			parent:     best,
-			minfreelen: best.prefix.Bits() + 1,
+			minfreelen: best.prefix.Bits() + 2,
 		}
 		best = best.lo
 	}
 
-	best.fixMinFreeAll()
+	best.fixMinFree()
+	tofix.fixMinFreeAll()
+
 	return best
 }
 
@@ -142,26 +146,25 @@ func (t *tree) fixMinFree() {
 	}
 	if t.Leaf() {
 		t.minfreelen = t.prefix.Addr().BitLen() + 1
+		return
 	}
 	lofree := t.lo.calcfreelen(t)
 	hifree := t.hi.calcfreelen(t)
 	minfreelen := max(min(lofree, hifree), t.prefix.Bits()+1)
 
-	if t.minfreelen != minfreelen {
-		//log.Printf("lo:%v, hi:%v\n", fixfree.lo == nil, fixfree.hi == nil)
-		//log.Printf("Fixing space for %q, lo: %d, hi: %d, old: %d, new: %d", fixfree.prefix, lofree, hifree, fixfree.minfreelen, minfreelen)
-		t.minfreelen = minfreelen
-	}
+	//if t.minfreelen != minfreelen {
+	//	log.Printf("lo:%v, hi:%v\n", t.lo == nil, t.hi == nil)
+	//	log.Printf("Fixing space for %q, lo: %d, hi: %d, old: %d, new: %d", t.prefix, lofree, hifree, t.minfreelen, minfreelen)
+	//}
+
+	t.minfreelen = minfreelen
 }
 func (t *tree) fixMinFreeAll() {
 	if t == nil {
 		return
 	}
-	if t.Leaf() {
-		t.minfreelen = t.prefix.Addr().BitLen() + 1
-	}
 
-	fixfree := t.parent
+	fixfree := t
 
 	for fixfree != nil {
 		fixfree.fixMinFree()