[AArch64][jdk8] IO java workload has significant overhead without any clients.

Continue our experiments on AArch64. We saw strange thing on io workloads. They take awful count of time. I compare the same run on x86 and it is fine.

ReadWrite.java the simplest one thread java application (MyFile.txt is text 350 MB file)

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.FileReader;
import java.io.IOException;

public class ReadWrite {
.
    public static void main(String[] args) {
        try {
            FileReader reader = new FileReader("MyFile.txt");
            FileWriter writer = new FileWriter("MyFile2.txt", true);

            BufferedReader bufferedReader = new BufferedReader(reader);
            BufferedWriter bufferedWriter = new BufferedWriter(writer);

            String line;
            while ((line = bufferedReader.readLine()) != null) {
                bufferedWriter.write(line);
                bufferedWriter.newLine();
            }
            reader.close();
            writer.close();

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

Original run without DynamoRIO took ~2 secs. x86 with DynamoRIO took about 3 secs BUT AArch64 with DRIO took 14 minutes (420x overhead) :((

perf hotspots looks

opcodes statistics

Top 15 opcode execution counts in 64-bit AArch64 mode:
   90371625 : movz
  109692827 : cbz
  119677065 : ldrb
  141852747 : ldp
  149865875 : stp
  150764846 : sub
  186207835 : ubfm
  257289620 : str
  311057147 : orr
  372462682 : ldrsb
  373357880 : strh
  379415317 : strb
  736110803 : ldrh
  760824735 : ldr
  2145521407 : subs
  2182566199 : bcond
  2473296771 : add

Also I've tried to check c++ native version on AArch64 and it looks fine

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main () {
  string line;
  ifstream myfile ("MyFile.txt");
  ofstream myfile2 ("MyFile2.txt");
  if (myfile.is_open() && myfile2.is_open())
  {
    while ( getline (myfile,line) )
    {
      myfile2 <<  line << '\n';
    }
    myfile.close();
    myfile2.close();
  }

  else cout << "Unable to open file";

  return 0;
}

opcodes statistics

Top 15 opcode execution counts in 64-bit AArch64 mode:
   38881409 : sub
   41657277 : bl
   43253273 : cbz
   44942292 : cbnz
   48018122 : br
   54446025 : ret
   63293933 : ldur
   64014752 : movz
   64051241 : adrp
   99217398 : stp
  124038866 : bcond
  127033323 : subs
  127577743 : ldp
  148219600 : str
  211563739 : add
  222393285 : orr
  353538698 : ldr

Maybe you have ideas what could be wrong here? Why do we have such difference between x86 and AArch64 on such java workloads? Thanks, Kirill