private void writeLong(OplogFile olf, long v) {
      ByteBuffer bb = olf.writeBuf;
      if (8 > bb.remaining()) {
        flushNoSync();
      }
      bb.putLong(v);
    }
How many bytes it will be when serialized
geode-core/src/main/java/org/apache/geode/internal/cache/Oplog.java