commit some suggestions

Signed-off-by: Leavrth <jianjun.liao@outlook.com>

br/pkg/restore/log_client.go

@@ -174,6 +174,8 @@ func (rc *logFileManager) createMetaIterOver(ctx context.Context, s storage.Exte
 		}
 		return meta, nil
 	}
+	// TODO: maybe we need to be able to adjust the concurrency to download files,
+	// which currently is the same as the chunk size
 	reader := iter.Transform(namesIter, readMeta,
 		iter.WithChunkSize(rc.metadataDownloadBatchSize), iter.WithConcurrency(rc.metadataDownloadBatchSize))
 	return reader, nil

br/pkg/task/common.go

@@ -93,7 +93,7 @@ const (
 	flagCipherKeyFile = "crypter.key-file"
 
 	flagMetadataDownloadBatchSize    = "metadata-download-batch-size"
-	defaultMetadataDownloadBatchSize = 64
+	defaultMetadataDownloadBatchSize = 128
 
 	unlimited           = 0
 	crypterAES128KeyLen = 16
@@ -303,6 +303,8 @@ func DefineCommonFlags(flags *pflag.FlagSet) {
 	flags.Uint(flagMetadataDownloadBatchSize, defaultMetadataDownloadBatchSize,
 		"the batch size of downloading metadata, such as log restore metadata for truncate or restore")
 
+	_ = flags.MarkHidden(flagMetadataDownloadBatchSize)
+
 	storage.DefineFlags(flags)
 }