bloblru: Upgrade to hashicorp/golang-lru/v2

The new genericized LRU cache no longer needs to have the IDs separately
allocated:

name   old time/op    new time/op    delta
Add-8     494ns ± 2%     388ns ± 2%  -21.46%  (p=0.000 n=10+9)

name   old alloc/op   new alloc/op   delta
Add-8      176B ± 0%      152B ± 0%  -13.64%  (p=0.000 n=10+10)

name   old allocs/op  new allocs/op  delta
Add-8      5.00 ± 0%      3.00 ± 0%  -40.00%  (p=0.000 n=10+10)

go.mod

@@ -9,7 +9,7 @@ require (
 	github.com/elithrar/simple-scrypt v1.3.0
 	github.com/go-ole/go-ole v1.2.6
 	github.com/google/go-cmp v0.5.9
-	github.com/hashicorp/golang-lru v0.5.4
+	github.com/hashicorp/golang-lru/v2 v2.0.1
 	github.com/juju/ratelimit v1.0.2
 	github.com/klauspost/compress v1.15.9
 	github.com/kurin/blazer v0.5.4-0.20211030221322-ba894c124ac6

go.sum

@@ -109,8 +109,8 @@ github.com/googleapis/enterprise-certificate-proxy v0.2.0 h1:y8Yozv7SZtlU//QXbez
 github.com/googleapis/enterprise-certificate-proxy v0.2.0/go.mod h1:8C0jb7/mgJe/9KK8Lm7X9ctZC2t60YyIpYEI16jx0Qg=
 github.com/googleapis/gax-go/v2 v2.7.0 h1:IcsPKeInNvYi7eqSaDjiZqDDKu5rsmunY0Y1YupQSSQ=
 github.com/googleapis/gax-go/v2 v2.7.0/go.mod h1:TEop28CZZQ2y+c0VxMUmu1lV+fQx57QpBWsYpwqHJx8=
-github.com/hashicorp/golang-lru v0.5.4 h1:YDjusn29QI/Das2iO9M0BHnIbxPeyuCHsjMW+lJfyTc=
-github.com/hashicorp/golang-lru v0.5.4/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
+github.com/hashicorp/golang-lru/v2 v2.0.1 h1:5pv5N1lT1fjLg2VQ5KWc7kmucp2x/kvFOnxuVTqZ6x4=
+github.com/hashicorp/golang-lru/v2 v2.0.1/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyfM2/ZepoAG6RGpeM=
 github.com/ianlancetaylor/demangle v0.0.0-20210905161508-09a460cdf81d/go.mod h1:aYm2/VgdVmcIU8iMfdMvDMsRAQjcfZSKFby6HOFvi/w=
 github.com/inconshreveable/mousetrap v1.0.1 h1:U3uMjPSQEBMNp1lFxmllqCPM6P5u/Xq7Pgzkat/bFNc=
 github.com/inconshreveable/mousetrap v1.0.1/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=

internal/bloblru/cache.go

@@ -6,7 +6,7 @@ import (
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/restic"
 
-	"github.com/hashicorp/golang-lru/simplelru"
+	"github.com/hashicorp/golang-lru/v2/simplelru"
 )
 
 // Crude estimate of the overhead per blob: a SHA-256, a linked list node
@@ -17,7 +17,7 @@ const overhead = len(restic.ID{}) + 64
 // It is safe for concurrent access.
 type Cache struct {
 	mu sync.Mutex
-	c  *simplelru.LRU
+	c  *simplelru.LRU[restic.ID, []byte]
 
 	free, size int // Current and max capacity, in bytes.
 }
@@ -33,7 +33,7 @@ func New(size int) *Cache {
 	// The actual maximum will be smaller than size/overhead, because we
 	// evict entries (RemoveOldest in add) to maintain our size bound.
 	maxEntries := size / overhead
-	lru, err := simplelru.NewLRU(maxEntries, c.evict)
+	lru, err := simplelru.NewLRU[restic.ID, []byte](maxEntries, c.evict)
 	if err != nil {
 		panic(err) // Can only be maxEntries <= 0.
 	}
@@ -55,24 +55,21 @@ func (c *Cache) Add(id restic.ID, blob []byte) (old []byte) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
-	var key interface{} = id
-
-	if c.c.Contains(key) { // Doesn't update the recency list.
+	if c.c.Contains(id) { // Doesn't update the recency list.
 		return
 	}
 
 	// This loop takes at most min(maxEntries, maxchunksize/overhead)
 	// iterations.
 	for size > c.free {
-		_, val, _ := c.c.RemoveOldest()
-		b := val.([]byte)
+		_, b, _ := c.c.RemoveOldest()
 		if cap(b) > cap(old) {
 			// We can only return one buffer, so pick the largest.
 			old = b
 		}
 	}
 
-	c.c.Add(key, blob)
+	c.c.Add(id, blob)
 	c.free -= size
 
 	return old
@@ -80,17 +77,15 @@ func (c *Cache) Add(id restic.ID, blob []byte) (old []byte) {
 
 func (c *Cache) Get(id restic.ID) ([]byte, bool) {
 	c.mu.Lock()
-	value, ok := c.c.Get(id)
+	blob, ok := c.c.Get(id)
 	c.mu.Unlock()
 
 	debug.Log("bloblru.Cache: get %v, hit %v", id, ok)
 
-	blob, ok := value.([]byte)
 	return blob, ok
 }
 
-func (c *Cache) evict(key, value interface{}) {
-	blob := value.([]byte)
+func (c *Cache) evict(key restic.ID, blob []byte) {
 	debug.Log("bloblru.Cache: evict %v, %d bytes", key, cap(blob))
 	c.free += cap(blob) + overhead
 }

internal/bloblru/cache_test.go

@@ -1,6 +1,7 @@
 package bloblru
 
 import (
+	"math/rand"
 	"testing"
 
 	"github.com/restic/restic/internal/restic"
@@ -50,3 +51,29 @@ func TestCache(t *testing.T) {
 	rtest.Equals(t, cacheSize, c.size)
 	rtest.Equals(t, cacheSize, c.free)
 }
+
+func BenchmarkAdd(b *testing.B) {
+	const (
+		MiB    = 1 << 20
+		nblobs = 64
+	)
+
+	c := New(64 * MiB)
+
+	buf := make([]byte, 8*MiB)
+	ids := make([]restic.ID, nblobs)
+	sizes := make([]int, nblobs)
+
+	r := rand.New(rand.NewSource(100))
+	for i := range ids {
+		r.Read(ids[i][:])
+		sizes[i] = r.Intn(8 * MiB)
+	}
+
+	b.ResetTimer()
+	b.ReportAllocs()
+
+	for i := 0; i < b.N; i++ {
+		c.Add(ids[i%nblobs], buf[:sizes[i%nblobs]])
+	}
+}