fix: pre-allocate certain slices with expected capacity (#12044)

Avoids append() based tiny allocations on known
allocated slices repeated access.

cmd/erasure-sets.go

@@ -612,7 +612,7 @@ func (s *erasureSets) StorageInfo(ctx context.Context) (StorageInfo, []error) {
 		storageInfo.Disks = append(storageInfo.Disks, lstorageInfo.Disks...)
 	}
 
-	var errs []error
+	errs := make([]error, 0, len(s.sets)*s.setDriveCount)
 	for i := range s.sets {
 		errs = append(errs, storageInfoErrs[i]...)
 	}

cmd/format-erasure.go

@@ -663,7 +663,7 @@ func formatErasureV3Check(reference *formatErasureV3, format *formatErasureV3) e
 func initErasureMetaVolumesInLocalDisks(storageDisks []StorageAPI, formats []*formatErasureV3) error {
 
 	// Compute the local disks eligible for meta volumes (re)initialization
-	var disksToInit []StorageAPI
+	disksToInit := make([]StorageAPI, 0, len(storageDisks))
 	for index := range storageDisks {
 		if formats[index] == nil || storageDisks[index] == nil || !storageDisks[index].IsLocal() {
 			// Ignore create meta volume on disks which are not found or not local.

cmd/namespace-lock.go

@@ -1,5 +1,5 @@
 /*
- * MinIO Cloud Storage, (C) 2016, 2017, 2018, 2019 MinIO, Inc.
+ * MinIO Cloud Storage, (C) 2016-2021 MinIO, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -211,16 +211,18 @@ func (li *localLockInstance) GetLock(ctx context.Context, timeout *dynamicTimeou
 	lockSource := getSource(2)
 	start := UTCNow()
 	const readLock = false
-	var success []int
+	success := make([]int, len(li.paths))
 	for i, path := range li.paths {
 		if !li.ns.lock(ctx, li.volume, path, lockSource, li.opsID, readLock, timeout.Timeout()) {
 			timeout.LogFailure()
-			for _, sint := range success {
-				li.ns.unlock(li.volume, li.paths[sint], readLock)
+			for si, sint := range success {
+				if sint == 1 {
+					li.ns.unlock(li.volume, li.paths[si], readLock)
+				}
 			}
 			return nil, OperationTimedOut{}
 		}
-		success = append(success, i)
+		success[i] = 1
 	}
 	timeout.LogSuccess(UTCNow().Sub(start))
 	return ctx, nil
@@ -239,16 +241,18 @@ func (li *localLockInstance) GetRLock(ctx context.Context, timeout *dynamicTimeo
 	lockSource := getSource(2)
 	start := UTCNow()
 	const readLock = true
-	var success []int
+	success := make([]int, len(li.paths))
 	for i, path := range li.paths {
 		if !li.ns.lock(ctx, li.volume, path, lockSource, li.opsID, readLock, timeout.Timeout()) {
 			timeout.LogFailure()
-			for _, sint := range success {
-				li.ns.unlock(li.volume, li.paths[sint], readLock)
+			for si, sint := range success {
+				if sint == 1 {
+					li.ns.unlock(li.volume, li.paths[si], readLock)
+				}
 			}
 			return nil, OperationTimedOut{}
 		}
-		success = append(success, i)
+		success[i] = 1
 	}
 	timeout.LogSuccess(UTCNow().Sub(start))
 	return ctx, nil

cmd/xl-storage-format-v2.go

@@ -1147,7 +1147,7 @@ func (z xlMetaV2) TotalSize() int64 {
 // showPendingDeletes is set to true if ListVersions needs to list objects marked deleted
 // but waiting to be replicated
 func (z xlMetaV2) ListVersions(volume, path string) ([]FileInfo, time.Time, error) {
-	var versions []FileInfo
+	versions := make([]FileInfo, 0, len(z.Versions))
 	var err error
 
 	for _, version := range z.Versions {