What comes from using a single kernel thread for all java threads...
>From: Scott Comer <###@###.###>

i used the attached code to open a connection to the tcp echo service
(localhost, port 7) and write 5 bytes of data, and then read back 5
bytes (and compare it), and then close the connection.

i wrote the code to try two different approaches: the first creates a
process to do the above and then waits for it to complete. it does this
50 times. the second approach creates 50 processes to do the above, and
doesn't wait for them to complete. either way, when 50 connections have
been created, written, read, and closed, the program exits (because
there are no more non-daemon processes).

the bug is that approach one (50 processes one at a time) takes 9 wall
seconds, while the second approach takes 2 minutes and 26 seconds of
wall time.

per-connection, that's 180 milliseconds vs. 2.92 seconds.

the code as encloseed executes approach two. to test approach one, find
the following text: "//fc.join();" and remove the comment characters
"//" from the front.

to compile and execute:

javac MainClient.java
java MainClient

seems a little high to me. actually, the 180 milliseconds seems high to
me.

scott out

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Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Content-Disposition: inline; filename="MainClient.java"

import java.net.*;
import java.io.*;

class MainClient
{
public static void main(String[] args)
{
System.out.println("MainClient starting up...");

try
{
InetAddress myAddr = InetAddress.getByName("localhost");

for (int i = 0; i < 50; i++)
{
FooClient fc = new FooClient(myAddr, 7);
fc.start();
//fc.join();
}
}
catch (Exception e)
{
System.out.println("MainClient exception:");
System.out.println(e);
}

System.out.println("MainClient done.");
}
}

class FooClient extends Thread
{
InetAddress fc_address;
int fc_port;

public FooClient(InetAddress address, int port)
{
fc_address = address;
fc_port = port;
}

public boolean expecting(InputStream input, int b)
throws IOException
{
int a = input.read();

if (a != b)
{
System.out.println(
this + " got " + a + " but expected " + b + ".");
return false;
}

return true;
}

public void run()
{
try
{
Socket fc_socket = new Socket(fc_address, fc_port);

OutputStream output = fc_socket.getOutputStream();

output.write('t');
output.write('e');
output.write('s');
output.write('t');
output.write('\\n');
output.flush();

InputStream input = fc_socket.getInputStream();

boolean itWorked = expecting(input, 't') &&
expecting(input, 'e') &&
expecting(input, 's') &&
expecting(input, 't') &&
expecting(input, '\\n');

fc_socket.close();

System.out.println(this + " done.");
}
catch (Exception e)
{
System.out.println(this + " FooClient run exception:");
System.out.println(e);
}
}
}

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