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improve allocation performance by tracking available space in subtrees

This commit is contained in:
Johannes Kimmel 2023-11-13 18:56:32 +01:00
parent 822a8039b1
commit 4d8620ebd7
2 changed files with 146 additions and 29 deletions
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125
ipalloc/ipalloc.go
View File

@ -5,14 +5,16 @@ import (
"log"
"net/netip"
"slices"
"strings"
"sync"
)
type tree struct {
prefix netip.Prefix
lo *tree
hi *tree
parent *tree
prefix netip.Prefix
lo *tree
hi *tree
parent *tree
minfreelen int
}
func (t *tree) Prefix() netip.Prefix {
@ -71,33 +73,32 @@ func (t *tree) FindBestPrefixLen(bits int) *tree {
// already taken
return nil
}
//log.Println("testing", t.prefix)
if t.minfreelen > bits {
return nil
}
if t.prefix.Bits() >= bits {
//log.Println("too long", t.prefix)
return nil
}
var best *tree
if !t.Full() {
lobest := t.lo.FindBestPrefixLen(bits)
hibest := t.hi.FindBestPrefixLen(bits)
switch {
case lobest == nil:
best = hibest
case hibest == nil:
best = lobest
case lobest.minfreelen >= hibest.minfreelen:
best = lobest
default:
best = hibest
}
if best == nil {
best = t
}
better := func(t1, t2 *tree) *tree {
switch {
case t1 == nil:
return t2
case t2 == nil:
return t1
case t1.prefix.Bits() >= t2.prefix.Bits():
return t1
default:
return t2
}
}
best = better(best, t.lo.FindBestPrefixLen(bits))
best = better(best, t.hi.FindBestPrefixLen(bits))
return best
}
@ -114,8 +115,9 @@ func (t *tree) Alloc(bits int) *tree {
// the first insert can be into a new hi branch
if best.lo != nil {
best.hi = &tree{
prefix: SplitPrefixHi(best.prefix),
parent: best,
prefix: SplitPrefixHi(best.prefix),
parent: best,
minfreelen: best.prefix.Bits() + 1,
}
best = best.hi
}
@ -123,15 +125,57 @@ func (t *tree) Alloc(bits int) *tree {
// the rest of the inserts are always into the lo branch
for best.prefix.Bits() < bits {
best.lo = &tree{
prefix: SplitPrefixLo(best.prefix),
parent: best,
prefix: SplitPrefixLo(best.prefix),
parent: best,
minfreelen: best.prefix.Bits() + 1,
}
best = best.lo
}
best.fixMinFreeAll()
return best
}
func (t *tree) fixMinFree() {
if t == nil {
return
}
if t.Leaf() {
t.minfreelen = t.prefix.Addr().BitLen() + 1
}
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
}
}
func (t *tree) fixMinFreeAll() {
if t == nil {
return
}
if t.Leaf() {
t.minfreelen = t.prefix.Addr().BitLen() + 1
}
fixfree := t.parent
for fixfree != nil {
fixfree.fixMinFree()
fixfree = fixfree.parent
}
}
func (t *tree) calcfreelen(parent *tree) int {
if t == nil {
return parent.prefix.Bits() + 1
}
return t.minfreelen
}
func (t *tree) Insert(p netip.Prefix) *tree {
t = t.FindBestPrefix(p)
@ -150,6 +194,7 @@ func (t *tree) Insert(p netip.Prefix) *tree {
return nil
}
}
t.fixMinFreeAll()
return t
}
@ -184,12 +229,38 @@ func (t *tree) Dealloc(p netip.Prefix) error {
}
}
match.fixMinFree()
match = match.parent
}
return nil
}
func (t *tree) Dot() string {
var buf strings.Builder
fmt.Fprintln(&buf, "strict digraph {")
t.Walk(func(t *tree) bool {
printEdge := func(parent, child *tree) {
if child == nil {
return
}
fmt.Fprintf(&buf, "\t%q -> %q;\n", parent.prefix, child.prefix)
}
fmt.Fprintf(&buf, "\t%q [shape=none label=<<table border=\"0\" cellspacing=\"0\" cellborder=\"1\"><tr><td>prefix</td><td>%s</td></tr><tr><td>minfreelen</td><td>%d</td></tr></table>>];\n", t.prefix, t.prefix, t.minfreelen)
printEdge(t, t.lo)
printEdge(t, t.hi)
return true
})
fmt.Fprintln(&buf, "}")
return buf.String()
}
type DB struct {
sync.Mutex
provisions *tree

50
ipalloc/ipalloc_test.go
View File

@ -22,6 +22,32 @@ func TestSplitPrefix(t *testing.T) {
}
}
func TestTreeAllocSmall(t *testing.T) {
tests := []struct {
bits int
best string
}{
{32, "0.0.0.0/32"},
{32, "0.0.0.1/32"},
{31, "0.0.0.2/31"},
{32, "0.0.0.4/32"},
}
root := &tree{prefix: netip.MustParsePrefix("0.0.0.0/28")}
for _, test := range tests {
//t.Log("searching for", test.bits)
best := root.Alloc(test.bits)
if best == nil {
log.Print(root.Dot())
t.Fatal(root, test.bits)
}
//t.Log(test, "->", best.prefix)
if best.prefix != netip.MustParsePrefix(test.best) {
log.Print(root.Dot())
t.Fatal(root, test.bits, best.prefix.String())
}
}
}
func TestTreeAlloc(t *testing.T) {
tests := []struct {
bits int
@ -42,10 +68,10 @@ func TestTreeAlloc(t *testing.T) {
t.Fatal(root, test.bits)
}
if best.prefix != netip.MustParsePrefix(test.best) {
log.Print(root.Dot())
t.Fatal(root, test.bits, best.prefix.String())
}
}
}
func TestTreeDealloc(t *testing.T) {
@ -177,8 +203,28 @@ func TestInsert(t *testing.T) {
}
}
func expectAlloc(t *testing.T, root *tree, bits int, expect string) {
if alloc := root.Alloc(bits); alloc.prefix != netip.MustParsePrefix(expect) {
t.Logf("allocating %d bits failed: got %s, want %s", bits, alloc.prefix, expect)
t.Log("graph:\n", root.Dot())
t.Fatal()
}
}
func TestAllocDealloc(t *testing.T) {
root := &tree{prefix: netip.MustParsePrefix("0.0.0.0/30")}
expectAlloc(t, root, 31, "0.0.0.0/31")
expectAlloc(t, root, 32, "0.0.0.2/32")
if err := root.Dealloc(netip.MustParsePrefix("0.0.0.0/31")); err != nil {
t.Fatalf("%s", err)
}
expectAlloc(t, root, 32, "0.0.0.3/32")
expectAlloc(t, root, 32, "0.0.0.0/32")
expectAlloc(t, root, 32, "0.0.0.1/32")
}
func BenchmarkFill(b *testing.B) {
root := &tree{prefix: netip.MustParsePrefix("0.0.0.0/20")}
root := &tree{prefix: netip.MustParsePrefix("0.0.0.0/16")}
for {
if alloc := root.Alloc(32); alloc == nil {
break