perf(blooms): mempool no longer zeroes out buffers unnecessarily

pkg/util/mempool/pool.go

@@ -64,15 +64,6 @@ func (s *slab) get(size int) ([]byte, error) {
 		return nil, errSlabExhausted
 	}
 
-	// Taken from https://github.com/ortuman/nuke/blob/main/monotonic_arena.go#L37-L48
-	// This piece of code will be translated into a runtime.memclrNoHeapPointers
-	// invocation by the compiler, which is an assembler optimized implementation.
-	// Architecture specific code can be found at src/runtime/memclr_$GOARCH.s
-	// in Go source (since https://codereview.appspot.com/137880043).
-	for i := range buf {
-		buf[i] = 0
-	}
-
 	return buf[:size], nil
 }
 

pkg/util/mempool/pool_test.go

@@ -8,6 +8,8 @@ import (
 	"unsafe"
 
 	"github.com/stretchr/testify/require"
+
+	"github.com/grafana/loki/v3/pkg/util/flagext"
 )
 
 func TestMemPool(t *testing.T) {
@@ -43,24 +45,6 @@ func TestMemPool(t *testing.T) {
 		require.Equal(t, 512, cap(res))
 	})
 
-	t.Run("buffer is cleared when returned", func(t *testing.T) {
-		pool := New("test", []Bucket{
-			{Size: 1, Capacity: 64},
-		}, nil)
-		res, err := pool.Get(8)
-		require.NoError(t, err)
-		require.Equal(t, 8, len(res))
-		source := []byte{0, 1, 2, 3, 4, 5, 6, 7}
-		copy(res, source)
-
-		pool.Put(res)
-
-		res, err = pool.Get(8)
-		require.NoError(t, err)
-		require.Equal(t, 8, len(res))
-		require.Equal(t, make([]byte, 8), res)
-	})
-
 	t.Run("pool returns error when no buffer is available", func(t *testing.T) {
 		pool := New("test", []Bucket{
 			{Size: 1, Capacity: 64},
@@ -131,3 +115,25 @@ func TestMemPool(t *testing.T) {
 		t.Log("finished")
 	})
 }
+
+func BenchmarkSlab(b *testing.B) {
+	for _, sz := range []int{
+		1 << 10,   // 1KB
+		1 << 20,   // 1MB
+		128 << 20, // 128MB
+	} {
+		b.Run(flagext.ByteSize(uint64(sz)).String(), func(b *testing.B) {
+			slab := newSlab(sz, 1, newMetrics(nil, "test"))
+			slab.init()
+			b.ResetTimer()
+
+			for i := 0; i < b.N; i++ {
+				b, err := slab.get(sz)
+				if err != nil {
+					panic(err)
+				}
+				slab.put(b)
+			}
+		})
+	}
+}