optimize memory allocs during reconstruct (#4964)

The reedsolomon library now avoids allocations during reconstruction.
This change exploits that to reduce memory allocs and GC preasure during
healing and reading.

pkg/bpool/bpool_test.go

@@ -1,53 +0,0 @@
-/*
- * Minio Cloud Storage, (C) 2016 Minio, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package bpool
-
-import "testing"
-
-func TestBytePool(t *testing.T) {
-	size := int64(10)
-	n := 16
-	pool := NewBytePool(size, n)
-	enBlocks := make([][]byte, n)
-
-	// Allocates all the 16 byte slices in the pool.
-	alloc := func() {
-		for i := range enBlocks {
-			var err error
-			enBlocks[i], err = pool.Get()
-			if err != nil {
-				t.Fatal("expected nil, got", err)
-			}
-			// Make sure the slice length is as expected.
-			if len(enBlocks[i]) != int(size) {
-				t.Fatalf("expected size %d, got %d", len(enBlocks[i]), size)
-			}
-		}
-	}
-
-	// Allocate everything in the pool.
-	alloc()
-	// Any Get() will fail when the pool does not have any free buffer.
-	_, err := pool.Get()
-	if err == nil {
-		t.Fatalf("expected %s, got nil", err)
-	}
-	// Reset - so that all the buffers are marked as unused.
-	pool.Reset()
-	// Allocation of all the buffers in the pool should succeed now.
-	alloc()
-}