Add Put input readahead (#14084)

When reading input for PutObject or PutObjectPart add a readahead buffer for big inputs.

This will make network reads+hashing separate run async with erasure coding and writes. This will reduce overall latency in distributed setups where the input is from upstream and writes go to other servers.

We will read at 2 buffers ahead, meaning one will always be ready/waiting and one is currently being read from.

This improves PutObject and PutObjectParts for these cases.

cmd/erasure-object.go

@@ -29,6 +29,7 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/klauspost/readahead"
 	"github.com/minio/madmin-go"
 	"github.com/minio/minio-go/v7/pkg/tags"
 	"github.com/minio/minio/internal/bucket/lifecycle"
@@ -884,7 +885,21 @@ func (er erasureObjects) putObject(ctx context.Context, bucket string, object st
 		writers[i] = newBitrotWriter(disk, minioMetaTmpBucket, tempErasureObj, shardFileSize, DefaultBitrotAlgorithm, erasure.ShardSize())
 	}
 
-	n, erasureErr := erasure.Encode(ctx, data, writers, buffer, writeQuorum)
+	toEncode := io.Reader(data)
+	if data.Size() > bigFileThreshold {
+		// We use 2 buffers, so we always have a full buffer of input.
+		bufA := er.bp.Get()
+		bufB := er.bp.Get()
+		defer er.bp.Put(bufA)
+		defer er.bp.Put(bufB)
+		ra, err := readahead.NewReaderBuffer(data, [][]byte{bufA[:fi.Erasure.BlockSize], bufB[:fi.Erasure.BlockSize]})
+		if err == nil {
+			toEncode = ra
+			defer ra.Close()
+		}
+		logger.LogIf(ctx, err)
+	}
+	n, erasureErr := erasure.Encode(ctx, toEncode, writers, buffer, writeQuorum)
 	closeBitrotWriters(writers)
 	if erasureErr != nil {
 		return ObjectInfo{}, toObjectErr(erasureErr, minioMetaTmpBucket, tempErasureObj)