.

t/neo/storage/fs1/cmd/fstail/fstail.go

@@ -99,6 +99,7 @@ func fsTail(w io.Writer, path string, ntxn int) (err error) {
 		// read raw data inside transaction record
 		dataLen := txnh.DataLen()
 		if int64(cap(data)) < dataLen {
+			// TODO -> CeilPow2
 			data = make([]byte, dataLen)
 		} else {
 			data = data[:dataLen]

t/neo/storage/fs1/filestorage.go

@@ -19,6 +19,7 @@ package fs1
 import (
 	"encoding/binary"
 	"fmt"
+	"math/bits"
 	"io"
 	"os"
 
@@ -233,7 +234,7 @@ const (
 // LenPrev >= TxnHeaderFixSize	LenPrev was read/checked normally
 func (txnh *TxnHeader) Load(r io.ReaderAt /* *os.File */, pos int64, flags TxnLoadFlags) error {
 	if cap(txnh.workMem) < txnXHeaderFixSize {
-		txnh.workMem = make([]byte, txnXHeaderFixSize)
+		txnh.workMem = make([]byte, txnXHeaderFixSize, 256 /* to later avoid allocation for typical strings */)
 	}
 	work := txnh.workMem[:txnXHeaderFixSize]
 
@@ -314,7 +315,7 @@ func (txnh *TxnHeader) Load(r io.ReaderAt /* *os.File */, pos int64, flags TxnLo
 
 	// NOTE we encode whole strings length into len(.workMem)
 	if cap(txnh.workMem) < lstr {
-		txnh.workMem = make([]byte, lstr)
+		txnh.workMem = make([]byte, lstr, ceilPow2(uint64(lstr)))
 	} else {
 		txnh.workMem = txnh.workMem[:lstr]
 	}
@@ -548,13 +549,12 @@ func (dh *DataHeader) LoadBack(r io.ReaderAt /* *os.File */) error {
 		bug(dh, "LoadBack() on non-backpointer data header")
 	}
 
-	var xxx [8]byte	// XXX escapes ?
-	_, err := r.ReadAt(xxx[:], dh.Pos + DataHeaderSize)
+	_, err := r.ReadAt(dh.workMem[:8], dh.Pos + DataHeaderSize)
 	if err != nil {
 		return dh.err("read data", noEOF(err))
 	}
 
-	backPos := int64(binary.BigEndian.Uint64(xxx[:]))
+	backPos := int64(binary.BigEndian.Uint64(dh.workMem[0:]))
 	if backPos == 0 {
 		return io.EOF	// oid was deleted
 	}
@@ -635,6 +635,12 @@ func (dh *DataHeader) loadNext(r io.ReaderAt /* *os.File */, txnh *TxnHeader) er
 	return nil
 }
 
+// XXX move me out of here
+// ceilPow2 returns minimal y >= x, such as y = 2^i
+func ceilPow2(x uint64) uint64 {
+	return 1 << uint(bits.Len64(x))
+}
+
 // LoadData loads data for the data record taking backpointers into account
 // Data is loaded into *buf, which, if needed, is reallocated to hold all loading data size	XXX
 // NOTE on success dh state is changed to data header of original data transaction
@@ -654,7 +660,9 @@ func (dh *DataHeader) LoadData(r io.ReaderAt /* *os.File */, buf *[]byte)  error
 
 	// now read actual data
 	if int64(cap(*buf)) < dh.DataLen {
-		*buf = make([]byte, dh.DataLen)
+		// ceilPow2 reduces much allocations but is still not enogh to
+		// remove them all from BenchmarkIterate
+		*buf = make([]byte, dh.DataLen, ceilPow2(uint64(dh.DataLen)))
 	} else {
 		*buf = (*buf)[:dh.DataLen]
 	}