[#754] blobstor: Estimate compressability

Now it is possible to enable compressability estimation.
If data is likely uncompressable, it should reduce CPU time and memory.

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/blobstor/compression/bench_test.go

@@ -3,8 +3,10 @@ package compression
 import (
 	"crypto/rand"
 	"fmt"
+	"log"
 	"testing"
 
+	"github.com/klauspost/compress"
 	"github.com/stretchr/testify/require"
 )
 
@@ -47,3 +49,50 @@ func notSoRandomSlice(size, blockSize int) []byte {
 	}
 	return data
 }
+
+func BenchmarkCompressionRealVSEstimate(b *testing.B) {
+	var total float64 // to prevent from compiler optimizations
+	maxSize := 60 * 1024 * 1024
+	b.Run("estimate", func(b *testing.B) {
+		b.ResetTimer()
+
+		c := &Config{
+			Enabled: true,
+		}
+		require.NoError(b, c.Init())
+
+		for size := 1024; size <= maxSize; size *= 2 {
+			data := make([]byte, size)
+			_, err := rand.Reader.Read(data)
+			require.NoError(b, err)
+
+			b.StartTimer()
+			estimation := compress.Estimate(data)
+			total += estimation
+			b.StopTimer()
+		}
+	})
+
+	b.Run("compress", func(b *testing.B) {
+		b.ResetTimer()
+
+		c := &Config{
+			Enabled: true,
+		}
+		require.NoError(b, c.Init())
+
+		for size := 1024; size <= maxSize; size *= 2 {
+			data := make([]byte, size)
+			_, err := rand.Reader.Read(data)
+			require.NoError(b, err)
+
+			b.StartTimer()
+			maxSize := c.encoder.MaxEncodedSize(len(data))
+			compressed := c.encoder.EncodeAll(data, make([]byte, 0, maxSize))
+			total += float64(len(compressed)) / float64(len(data))
+			b.StopTimer()
+		}
+	})
+
+	log.Println(total)
+}

pkg/local_object_storage/blobstor/compression/compress.go

@@ -5,6 +5,7 @@ import (
 	"strings"
 
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	"github.com/klauspost/compress"
 	"github.com/klauspost/compress/zstd"
 )
 
@@ -13,6 +14,9 @@ type Config struct {
 	Enabled                    bool
 	UncompressableContentTypes []string
 
+	UseCompressEstimation       bool
+	CompressEstimationThreshold float64
+
 	encoder *zstd.Encoder
 	decoder *zstd.Decoder
 }
@@ -82,6 +86,17 @@ func (c *Config) Compress(data []byte) []byte {
 	if c == nil || !c.Enabled {
 		return data
 	}
+	if c.UseCompressEstimation {
+		estimated := compress.Estimate(data)
+		if estimated >= c.CompressEstimationThreshold {
+			return c.compress(data)
+		}
+		return data
+	}
+	return c.compress(data)
+}
+
+func (c *Config) compress(data []byte) []byte {
 	maxSize := c.encoder.MaxEncodedSize(len(data))
 	compressed := c.encoder.EncodeAll(data, make([]byte, 0, maxSize))
 	if len(data) < len(compressed) {