zstd: Add bigger default blocks (#469)

Keep 64K blocks for fastest, but do max size for others. Healthy compression increase for streams.

Author: klauspost

zstd/encoder_options.go

@@ -24,6 +24,7 @@ type encoderOptions struct {
 allLitEntropy bool
 customWindow bool
 customALEntropy bool
+customBlockSize bool
 lowMem bool
 dict *dict
 }
@@ -33,7 +34,7 @@ func (o *encoderOptions) setDefault() {
 concurrent: runtime.GOMAXPROCS(0),
 crc: true,
 single: nil,
-blockSize: 1 << 16,
+blockSize: maxCompressedBlockSize,
 windowSize: 8 << 20,
 level: SpeedDefault,
 allLitEntropy: true,
@@ -106,6 +107,7 @@ func WithWindowSize(n int) EOption {
 o.customWindow = true
 if o.blockSize > o.windowSize {
 o.blockSize = o.windowSize
+o.customBlockSize = true
 }
 return nil
 }
@@ -222,6 +224,9 @@ func WithEncoderLevel(l EncoderLevel) EOption {
 switch o.level {
 case SpeedFastest:
 o.windowSize = 4 << 20
+if !o.customBlockSize {
+o.blockSize = 1 << 16
+}
 case SpeedDefault:
 o.windowSize = 8 << 20
 case SpeedBetterCompression: