Preallocate (safe) slices when we know the size (#10459)

cmd/api-response.go

@@ -408,7 +408,7 @@ func getObjectLocation(r *http.Request, domains []string, bucket, object string)
 // generates ListBucketsResponse from array of BucketInfo which can be
 // serialized to match XML and JSON API spec output.
 func generateListBucketsResponse(buckets []BucketInfo) ListBucketsResponse {
-	var listbuckets []Bucket
+	listbuckets := make([]Bucket, 0, len(buckets))
 	var data = ListBucketsResponse{}
 	var owner = Owner{}
 
@@ -428,8 +428,7 @@ func generateListBucketsResponse(buckets []BucketInfo) ListBucketsResponse {
 
 // generates an ListBucketVersions response for the said bucket with other enumerated options.
 func generateListVersionsResponse(bucket, prefix, marker, versionIDMarker, delimiter, encodingType string, maxKeys int, resp ListObjectVersionsInfo) ListVersionsResponse {
-	var versions []ObjectVersion
+	versions := make([]ObjectVersion, 0, len(resp.Objects))
-	var prefixes []CommonPrefix
 	var owner = Owner{}
 	var data = ListVersionsResponse{}
 
@@ -473,6 +472,7 @@ func generateListVersionsResponse(bucket, prefix, marker, versionIDMarker, delim
 	data.VersionIDMarker = versionIDMarker
 	data.IsTruncated = resp.IsTruncated
 
+	prefixes := make([]CommonPrefix, 0, len(resp.Prefixes))
 	for _, prefix := range resp.Prefixes {
 		var prefixItem = CommonPrefix{}
 		prefixItem.Prefix = s3EncodeName(prefix, encodingType)
@@ -484,8 +484,7 @@ func generateListVersionsResponse(bucket, prefix, marker, versionIDMarker, delim
 
 // generates an ListObjectsV1 response for the said bucket with other enumerated options.
 func generateListObjectsV1Response(bucket, prefix, marker, delimiter, encodingType string, maxKeys int, resp ListObjectsInfo) ListObjectsResponse {
-	var contents []Object
+	contents := make([]Object, 0, len(resp.Objects))
-	var prefixes []CommonPrefix
 	var owner = Owner{}
 	var data = ListObjectsResponse{}
 
@@ -517,9 +516,10 @@ func generateListObjectsV1Response(bucket, prefix, marker, delimiter, encodingTy
 	data.Marker = s3EncodeName(marker, encodingType)
 	data.Delimiter = s3EncodeName(delimiter, encodingType)
 	data.MaxKeys = maxKeys
-
 	data.NextMarker = s3EncodeName(resp.NextMarker, encodingType)
 	data.IsTruncated = resp.IsTruncated
+
+	prefixes := make([]CommonPrefix, 0, len(resp.Prefixes))
 	for _, prefix := range resp.Prefixes {
 		var prefixItem = CommonPrefix{}
 		prefixItem.Prefix = s3EncodeName(prefix, encodingType)
@@ -531,8 +531,7 @@ func generateListObjectsV1Response(bucket, prefix, marker, delimiter, encodingTy
 
 // generates an ListObjectsV2 response for the said bucket with other enumerated options.
 func generateListObjectsV2Response(bucket, prefix, token, nextToken, startAfter, delimiter, encodingType string, fetchOwner, isTruncated bool, maxKeys int, objects []ObjectInfo, prefixes []string, metadata bool) ListObjectsV2Response {
-	var contents []Object
+	contents := make([]Object, 0, len(objects))
-	var commonPrefixes []CommonPrefix
 	var owner = Owner{}
 	var data = ListObjectsV2Response{}
 
@@ -585,6 +584,8 @@ func generateListObjectsV2Response(bucket, prefix, token, nextToken, startAfter,
 	data.ContinuationToken = base64.StdEncoding.EncodeToString([]byte(token))
 	data.NextContinuationToken = base64.StdEncoding.EncodeToString([]byte(nextToken))
 	data.IsTruncated = isTruncated
+
+	commonPrefixes := make([]CommonPrefix, 0, len(prefixes))
 	for _, prefix := range prefixes {
 		var prefixItem = CommonPrefix{}
 		prefixItem.Prefix = s3EncodeName(prefix, encodingType)

cmd/erasure-zones.go

@@ -637,8 +637,8 @@ func (z *erasureZones) ListObjectsV2(ctx context.Context, bucket, prefix, contin
 
 func (z *erasureZones) listObjectsNonSlash(ctx context.Context, bucket, prefix, marker, delimiter string, maxKeys int) (loi ListObjectsInfo, err error) {
 
-	var zonesEntryChs [][]FileInfoCh
+	zonesEntryChs := make([][]FileInfoCh, 0, len(z.zones))
-	var zonesListTolerancePerSet []int
+	zonesListTolerancePerSet := make([]int, 0, len(z.zones))
 
 	endWalkCh := make(chan struct{})
 	defer close(endWalkCh)
@@ -653,8 +653,8 @@ func (z *erasureZones) listObjectsNonSlash(ctx context.Context, bucket, prefix,
 	var eof bool
 	var prevPrefix string
 
-	var zonesEntriesInfos [][]FileInfo
+	zonesEntriesInfos := make([][]FileInfo, 0, len(zonesEntryChs))
-	var zonesEntriesValid [][]bool
+	zonesEntriesValid := make([][]bool, 0, len(zonesEntryChs))
 	for _, entryChs := range zonesEntryChs {
 		zonesEntriesInfos = append(zonesEntriesInfos, make([]FileInfo, len(entryChs)))
 		zonesEntriesValid = append(zonesEntriesValid, make([]bool, len(entryChs)))
@@ -756,9 +756,9 @@ func (z *erasureZones) listObjectsSplunk(ctx context.Context, bucket, prefix, ma
 
 	recursive := true
 
-	var zonesEntryChs [][]FileInfoCh
+	zonesEntryChs := make([][]FileInfoCh, 0, len(z.zones))
-	var zonesEndWalkCh []chan struct{}
+	zonesEndWalkCh := make([]chan struct{}, 0, len(z.zones))
-	var zonesListTolerancePerSet []int
+	zonesListTolerancePerSet := make([]int, 0, len(z.zones))
 
 	for _, zone := range z.zones {
 		entryChs, endWalkCh := zone.poolSplunk.Release(listParams{bucket, recursive, marker, prefix})
@@ -848,9 +848,9 @@ func (z *erasureZones) listObjects(ctx context.Context, bucket, prefix, marker,
 		recursive = false
 	}
 
-	var zonesEntryChs [][]FileInfoCh
+	zonesEntryChs := make([][]FileInfoCh, 0, len(z.zones))
-	var zonesEndWalkCh []chan struct{}
+	zonesEndWalkCh := make([]chan struct{}, 0, len(z.zones))
-	var zonesListTolerancePerSet []int
+	zonesListTolerancePerSet := make([]int, 0, len(z.zones))
 
 	for _, zone := range z.zones {
 		entryChs, endWalkCh := zone.pool.Release(listParams{bucket, recursive, marker, prefix})
@@ -1051,8 +1051,8 @@ func lexicallySortedEntryZoneVersions(zoneEntryChs [][]FileInfoVersionsCh, zoneE
 // mergeZonesEntriesVersionsCh - merges FileInfoVersions channel to entries upto maxKeys.
 func mergeZonesEntriesVersionsCh(zonesEntryChs [][]FileInfoVersionsCh, maxKeys int, zonesListTolerancePerSet []int) (entries FilesInfoVersions) {
 	var i = 0
-	var zonesEntriesInfos [][]FileInfoVersions
+	zonesEntriesInfos := make([][]FileInfoVersions, 0, len(zonesEntryChs))
-	var zonesEntriesValid [][]bool
+	zonesEntriesValid := make([][]bool, 0, len(zonesEntryChs))
 	for _, entryChs := range zonesEntryChs {
 		zonesEntriesInfos = append(zonesEntriesInfos, make([]FileInfoVersions, len(entryChs)))
 		zonesEntriesValid = append(zonesEntriesValid, make([]bool, len(entryChs)))
@@ -1082,8 +1082,8 @@ func mergeZonesEntriesVersionsCh(zonesEntryChs [][]FileInfoVersionsCh, maxKeys i
 // mergeZonesEntriesCh - merges FileInfo channel to entries upto maxKeys.
 func mergeZonesEntriesCh(zonesEntryChs [][]FileInfoCh, maxKeys int, zonesListTolerancePerSet []int) (entries FilesInfo) {
 	var i = 0
-	var zonesEntriesInfos [][]FileInfo
+	zonesEntriesInfos := make([][]FileInfo, 0, len(zonesEntryChs))
-	var zonesEntriesValid [][]bool
+	zonesEntriesValid := make([][]bool, 0, len(zonesEntryChs))
 	for _, entryChs := range zonesEntryChs {
 		zonesEntriesInfos = append(zonesEntriesInfos, make([]FileInfo, len(entryChs)))
 		zonesEntriesValid = append(zonesEntriesValid, make([]bool, len(entryChs)))
@@ -1218,9 +1218,9 @@ func (z *erasureZones) listObjectVersions(ctx context.Context, bucket, prefix, m
 		recursive = false
 	}
 
-	var zonesEntryChs [][]FileInfoVersionsCh
+	zonesEntryChs := make([][]FileInfoVersionsCh, 0, len(z.zones))
-	var zonesEndWalkCh []chan struct{}
+	zonesEndWalkCh := make([]chan struct{}, 0, len(z.zones))
-	var zonesListTolerancePerSet []int
+	zonesListTolerancePerSet := make([]int, 0, len(z.zones))
 	for _, zone := range z.zones {
 		entryChs, endWalkCh := zone.poolVersions.Release(listParams{bucket, recursive, marker, prefix})
 		if entryChs == nil {
@@ -1737,18 +1737,15 @@ func (z *erasureZones) Walk(ctx context.Context, bucket, prefix string, results
 		return nil
 	}
 
-	var zonesEntryChs [][]FileInfoCh
+	zonesEntryChs := make([][]FileInfoCh, 0, len(z.zones))
+	zoneDrivesPerSet := make([]int, 0, len(z.zones))
 	for _, zone := range z.zones {
 		zonesEntryChs = append(zonesEntryChs, zone.startMergeWalks(ctx, bucket, prefix, "", true, ctx.Done()))
-	}
-
-	var zoneDrivesPerSet []int
-	for _, zone := range z.zones {
 		zoneDrivesPerSet = append(zoneDrivesPerSet, zone.setDriveCount)
 	}
 
-	var zonesEntriesInfos [][]FileInfo
+	zonesEntriesInfos := make([][]FileInfo, 0, len(zonesEntryChs))
-	var zonesEntriesValid [][]bool
+	zonesEntriesValid := make([][]bool, 0, len(zonesEntryChs))
 	for _, entryChs := range zonesEntryChs {
 		zonesEntriesInfos = append(zonesEntriesInfos, make([]FileInfo, len(entryChs)))
 		zonesEntriesValid = append(zonesEntriesValid, make([]bool, len(entryChs)))
@@ -1779,23 +1776,20 @@ func (z *erasureZones) Walk(ctx context.Context, bucket, prefix string, results
 type HealObjectFn func(bucket, object, versionID string) error
 
 func (z *erasureZones) HealObjects(ctx context.Context, bucket, prefix string, opts madmin.HealOpts, healObject HealObjectFn) error {
-	var zonesEntryChs [][]FileInfoVersionsCh
-
 	endWalkCh := make(chan struct{})
 	defer close(endWalkCh)
 
+	zonesEntryChs := make([][]FileInfoVersionsCh, 0, len(z.zones))
+	zoneDrivesPerSet := make([]int, 0, len(z.zones))
+
 	for _, zone := range z.zones {
 		zonesEntryChs = append(zonesEntryChs,
 			zone.startMergeWalksVersions(ctx, bucket, prefix, "", true, endWalkCh))
-	}
-
-	var zoneDrivesPerSet []int
-	for _, zone := range z.zones {
 		zoneDrivesPerSet = append(zoneDrivesPerSet, zone.setDriveCount)
 	}
 
-	var zonesEntriesInfos [][]FileInfoVersions
+	zonesEntriesInfos := make([][]FileInfoVersions, 0, len(zonesEntryChs))
-	var zonesEntriesValid [][]bool
+	zonesEntriesValid := make([][]bool, 0, len(zonesEntryChs))
 	for _, entryChs := range zonesEntryChs {
 		zonesEntriesInfos = append(zonesEntriesInfos, make([]FileInfoVersions, len(entryChs)))
 		zonesEntriesValid = append(zonesEntriesValid, make([]bool, len(entryChs)))

cmd/fs-v1.go

@@ -502,13 +502,13 @@ func (fs *FSObjects) ListBuckets(ctx context.Context) ([]BucketInfo, error) {
 		atomic.AddInt64(&fs.activeIOCount, -1)
 	}()
 
-	var bucketInfos []BucketInfo
 	entries, err := readDir(fs.fsPath)
 	if err != nil {
 		logger.LogIf(ctx, errDiskNotFound)
 		return nil, toObjectErr(errDiskNotFound)
 	}
 
+	bucketInfos := make([]BucketInfo, 0, len(entries))
 	for _, entry := range entries {
 		// Ignore all reserved bucket names and invalid bucket names.
 		if isReservedOrInvalidBucket(entry, false) {

cmd/object-handlers.go

@@ -2557,7 +2557,7 @@ func (api objectAPIHandlers) CompleteMultipartUploadHandler(w http.ResponseWrite
 	}
 
 	// Complete parts.
-	var completeParts []CompletePart
+	completeParts := make([]CompletePart, 0, len(complMultipartUpload.Parts))
 	for _, part := range complMultipartUpload.Parts {
 		part.ETag = canonicalizeETag(part.ETag)
 		if isEncrypted {

cmd/peer-rest-client.go

@@ -829,8 +829,9 @@ func (client *peerRESTClient) ConsoleLog(logCh chan interface{}, doneCh <-chan s
 }
 
 func getRemoteHosts(endpointZones EndpointZones) []*xnet.Host {
-	var remoteHosts []*xnet.Host
+	peers := GetRemotePeers(endpointZones)
-	for _, hostStr := range GetRemotePeers(endpointZones) {
+	remoteHosts := make([]*xnet.Host, 0, len(peers))
+	for _, hostStr := range peers {
 		host, err := xnet.ParseHost(hostStr)
 		if err != nil {
 			logger.LogIf(GlobalContext, err)

cmd/peer-rest-server.go

@@ -47,7 +47,7 @@ func (s *peerRESTServer) GetLocksHandler(w http.ResponseWriter, r *http.Request)
 
 	ctx := newContext(r, w, "GetLocks")
 
-	var llockers []map[string][]lockRequesterInfo
+	llockers := make([]map[string][]lockRequesterInfo, 0, len(globalLockServers))
 	for _, llocker := range globalLockServers {
 		llockers = append(llockers, llocker.DupLockMap())
 	}

cmd/xl-storage.go

@@ -654,7 +654,7 @@ func listVols(dirPath string) ([]VolInfo, error) {
 	if err != nil {
 		return nil, errDiskNotFound
 	}
-	var volsInfo []VolInfo
+	volsInfo := make([]VolInfo, 0, len(entries))
 	for _, entry := range entries {
 		if !HasSuffix(entry, SlashSeparator) || !isValidVolname(slashpath.Clean(entry)) {
 			// Skip if entry is neither a directory not a valid volume name.