util/buffer_pool, db: Reduce memory allocation

leveldb/db.go

@@ -319,7 +319,7 @@ func recoverTable(s *session, o *opt.Options) error {
  }()
 
  // Copy entries.
- tw := table.NewWriter(writer, o)
+ tw := table.NewWriter(writer, o, nil, 0)
  for iter.Next() {
  key := iter.Key()
  if validInternalKey(key) {

leveldb/db_compaction.go

@@ -389,7 +389,7 @@ func (b *tableCompactionBuilder) appendKV(key, value []byte) error {
 
  // Create new table.
  var err error
- b.tw, err = b.s.tops.create()
+ b.tw, err = b.s.tops.create(b.tableSize)
  if err != nil {
  return err
  }

leveldb/db_test.go

@@ -2539,7 +2539,7 @@ func TestDB_TableCompactionBuilder(t *testing.T) {
  value = bytes.Repeat([]byte{'0'}, 100)
  )
  for i := 0; i < 2; i++ {
- tw, err := s.tops.create()
+ tw, err := s.tops.create(0)
  if err != nil {
  t.Fatal(err)
  }

leveldb/table.go

@@ -366,7 +366,7 @@ type tOps struct {
 }
 
 // Creates an empty table and returns table writer.
-func (t *tOps) create() (*tWriter, error) {
+func (t *tOps) create(tSize int) (*tWriter, error) {
  fd := storage.FileDesc{Type: storage.TypeTable, Num: t.s.allocFileNum()}
  fw, err := t.s.stor.Create(fd)
  if err != nil {
@@ -376,13 +376,13 @@ func (t *tOps) create() (*tWriter, error) {
  t: t,
  fd: fd,
  w: fw,
- tw: table.NewWriter(fw, t.s.o.Options),
+ tw: table.NewWriter(fw, t.s.o.Options, t.bpool, tSize),
  }, nil
 }
 
 // Builds table from src iterator.
 func (t *tOps) createFrom(src iterator.Iterator) (f *tFile, n int, err error) {
- w, err := t.create()
+ w, err := t.create(0)
  if err != nil {
  return
  }
@@ -501,7 +501,6 @@ func (t *tOps) remove(fd storage.FileDesc) {
 // Closes the table ops instance. It will close all tables,
 // regadless still used or not.
 func (t *tOps) close() {
- t.bpool.Close()
  t.cache.Close()
  if t.bcache != nil {
  t.bcache.CloseWeak()

leveldb/table/table_test.go

@@ -47,7 +47,7 @@ var _ = testutil.Defer(func() {
  )
 
  // Building the table.
- tw := NewWriter(buf, o)
+ tw := NewWriter(buf, o, nil, 0)
  tw.Append([]byte("k01"), []byte("hello"))
  tw.Append([]byte("k02"), []byte("hello2"))
  tw.Append([]byte("k03"), bytes.Repeat([]byte{'x'}, 10000))
@@ -90,7 +90,7 @@ var _ = testutil.Defer(func() {
  buf := &bytes.Buffer{}
 
  // Building the table.
- tw := NewWriter(buf, o)
+ tw := NewWriter(buf, o, nil, 0)
  kv.Iterate(func(i int, key, value []byte) {
  tw.Append(key, value)
  })

leveldb/table/writer.go

@@ -146,6 +146,7 @@ type Writer struct {
  compression opt.Compression
  blockSize int
 
+ bpool *util.BufferPool
  dataBlock blockWriter
  indexBlock blockWriter
  filterBlock filterWriter
@@ -285,6 +286,16 @@ func (w *Writer) BytesLen() int {
 // after Close, but calling BlocksLen, EntriesLen and BytesLen
 // is still possible.
 func (w *Writer) Close() error {
+ defer func() {
+ if w.bpool != nil {
+ // Buffer.Bytes() returns [offset:] of the buffer.
+ // We need to Reset() so that the offset = 0, resulting
+ // in buf.Bytes() returning the whole allocated bytes.
+ w.dataBlock.buf.Reset()
+ w.bpool.Put(w.dataBlock.buf.Bytes())
+ }
+ }()
+
  if w.err != nil {
  return w.err
  }
@@ -351,14 +362,24 @@ func (w *Writer) Close() error {
 // NewWriter creates a new initialized table writer for the file.
 //
 // Table writer is not safe for concurrent use.
-func NewWriter(f io.Writer, o *opt.Options) *Writer {
+func NewWriter(f io.Writer, o *opt.Options, pool *util.BufferPool, size int) *Writer {
+ var bufBytes []byte
+ if pool == nil {
+ bufBytes = make([]byte, size)
+ } else {
+ bufBytes = pool.Get(size)
+ }
+ bufBytes = bufBytes[:0]
+
  w := &Writer{
  writer: f,
  cmp: o.GetComparer(),
  filter: o.GetFilter(),
  compression: o.GetCompression(),
  blockSize: o.GetBlockSize(),
  comparerScratch: make([]byte, 0),
+ bpool: pool,
+ dataBlock: blockWriter{buf: *util.NewBuffer(bufBytes)},
  }
  // data block
  w.dataBlock.restartInterval = o.GetBlockRestartInterval()