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digitalmars.D.learn - Socket server + thread: cpu usage

reply "Tim" <timvol ymail.com> writes:
Hi guys,

I've the following snipped:

TcpSocket oSocket = new TcpSocket(AddressFamily.INET);
oSocket.bind(new InternetAddress("127.0.0.1", 12345));
oSocket.blocking(false);
oSocket.listen(0);

while(true)
{
	try
	{
		Socket oRequestSocket = oSocket.accept();

		Request oRequest = new Request(oRequestSocket);
		oRequest.start(); // Start request thread
	}
	catch (SocketAcceptException oException)
	{
		Thread.yield();
	}
}

When I execute the code above, the while(true)-loop uses nearly 
100% (1 complete cpu). When I connect to the server multiple 
times (note that each Request-Thread has it's own 
while(oRequestSocket.isAlive)-loop) the cpu usage easily reaches 
120, 130... 200 and more cpu usage.

Is there anything I'm doing wrong? I don't want use blocking 
sockets... how to handle 100 or 1000 connections when the main 
server thread already consumes 1 cpu?
Apr 29 2014
next sibling parent reply "Adam D. Ruppe" <destructionator gmail.com> writes:
On Tuesday, 29 April 2014 at 17:16:33 UTC, Tim wrote:

 Is there anything I'm doing wrong?


You should be using a blocking socket. With them, the operating 
system will put your thread on hold until a new connection comes 
in. Without them, it will endlessly loop doing absolutely nothing 
except checking if a new connection is there yet. Horribly, 
horribly inefficient.
Apr 29 2014
next sibling parent reply "Tim" <timvol ymail.com> writes:
On Tuesday, 29 April 2014 at 17:19:41 UTC, Adam D. Ruppe wrote:

 On Tuesday, 29 April 2014 at 17:16:33 UTC, Tim wrote:

 Is there anything I'm doing wrong?


 You should be using a blocking socket. With them, the operating 
 system will put your thread on hold until a new connection 
 comes in. Without them, it will endlessly loop doing absolutely 
 nothing except checking if a new connection is there yet. 
 Horribly, horribly inefficient.


Alright, this would solve the server-cpu-usage-problem. But what 
about incoming connections? When I create a new thread and use 
non-blocking socket I've exactly the same problem. I can also 
solve this problem by using blocking sockets, but what happens if 
I do the following:

while(oMyBlockingSocket.isAlive)
{
     oMyBlockingSocket.receive(...);
}

... and close the connection on the client side? I would never 
receive anything and receive() waits never comes back or would 
this throw an exception or similar?
Apr 29 2014
parent reply "Tim" <timvol ymail.com> writes:
On Tuesday, 29 April 2014 at 17:35:08 UTC, Tim wrote:

 On Tuesday, 29 April 2014 at 17:19:41 UTC, Adam D. Ruppe wrote:

 On Tuesday, 29 April 2014 at 17:16:33 UTC, Tim wrote:

 Is there anything I'm doing wrong?


 You should be using a blocking socket. With them, the 
 operating system will put your thread on hold until a new 
 connection comes in. Without them, it will endlessly loop 
 doing absolutely nothing except checking if a new connection 
 is there yet. Horribly, horribly inefficient.


 Alright, this would solve the server-cpu-usage-problem. But 
 what about incoming connections? When I create a new thread and 
 use non-blocking socket I've exactly the same problem. I can 
 also solve this problem by using blocking sockets, but what 
 happens if I do the following:

 while(oMyBlockingSocket.isAlive)
 {
     oMyBlockingSocket.receive(...);
 }

 ... and close the connection on the client side? I would never 
 receive anything and receive() waits never comes back or would 
 this throw an exception or similar?


Sorry... I totally forgot... I can use SocketSet's as I already 
asked: 
http://forum.dlang.org/thread/ogghezngzrvvoqaoddbh forum.dlang.org#post-kivp3e:24jif:241:40digitalmars.com

... but I thought it's also possible using non blocking sockets 
by using Thread.yield().
Apr 29 2014
parent reply "Damian Day" <damianroyday gmail.com> writes:
On Tuesday, 29 April 2014 at 17:44:21 UTC, Tim wrote:

 On Tuesday, 29 April 2014 at 17:35:08 UTC, Tim wrote:

 On Tuesday, 29 April 2014 at 17:19:41 UTC, Adam D. Ruppe wrote:

 On Tuesday, 29 April 2014 at 17:16:33 UTC, Tim wrote:

 Is there anything I'm doing wrong?


 You should be using a blocking socket. With them, the 
 operating system will put your thread on hold until a new 
 connection comes in. Without them, it will endlessly loop 
 doing absolutely nothing except checking if a new connection 
 is there yet. Horribly, horribly inefficient.


 Alright, this would solve the server-cpu-usage-problem. But 
 what about incoming connections? When I create a new thread 
 and use non-blocking socket I've exactly the same problem. I 
 can also solve this problem by using blocking sockets, but 
 what happens if I do the following:

 while(oMyBlockingSocket.isAlive)
 {
    oMyBlockingSocket.receive(...);
 }

 ... and close the connection on the client side? I would never 
 receive anything and receive() waits never comes back or would 
 this throw an exception or similar?


 Sorry... I totally forgot... I can use SocketSet's as I already 
 asked: 
 http://forum.dlang.org/thread/ogghezngzrvvoqaoddbh forum.dlang.org#post-kivp3e:24jif:241:40digitalmars.com

 ... but I thought it's also possible using non blocking sockets 
 by using Thread.yield().


You want to add something like this to your while loop:
Thread.sleep( dur!("msecs")( 20 ) );
That will give back some time to the CPU.
Apr 30 2014
parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 04/30/2014 04:24 PM, Damian Day wrote:


 Thread.sleep( dur!("msecs")( 20 ) );


Going off topic, the UFCS syntax makes that code much more readable. :)

     Thread.sleep(20.msecs);

Ali
Apr 30 2014
prev sibling parent reply "Tim" <timvol ymail.com> writes:
On Tuesday, 29 April 2014 at 17:19:41 UTC, Adam D. Ruppe wrote:

 On Tuesday, 29 April 2014 at 17:16:33 UTC, Tim wrote:

 Is there anything I'm doing wrong?


 You should be using a blocking socket. With them, the operating 
 system will put your thread on hold until a new connection 
 comes in. Without them, it will endlessly loop doing absolutely 
 nothing except checking if a new connection is there yet. 
 Horribly, horribly inefficient.


Blocking sockets are now working as expected, but I've one 
problem. When I do the following in my server-accept-thread:

while (m_oSocket.isAlive)
{
	oSocketSet.reset();
	oSocketSet.add(m_oSocket);

	nAcceptedSockets = Socket.select(oSocketSet, null, null, 
25.msecs);

	if (nAcceptedSockets > 0)
	{
		// Do something...
	}

}

... and the following in my client:

void connect()
{
	m_oSocket = new TcpSocket(AddressFamily.INET);
	m_oSocket.connect(new InternetAddress("127.0.0.1", 12345));
}

The CPU usage is low as long as my connect is connected. When I 
disconnect the client using the following few lines:

void disconnect()
{
	m_oSocket.shutdown(SocketShutdown.BOTH);
	m_oSocket.close();
}

... the CPU usage goes up. I think that SocketShutdown.BOTH 
causes Socket.select to fail which results in an endless loop. 
Any suggestions how to handle that problem?

 Ali Çehreli: Thanks, didn't know that UFCS can also handle such 
constructs :)
May 01 2014
next sibling parent "Tim" <timvol ymail.com> writes:
On Thursday, 1 May 2014 at 08:08:37 UTC, Tim wrote:

 On Tuesday, 29 April 2014 at 17:19:41 UTC, Adam D. Ruppe wrote:

 On Tuesday, 29 April 2014 at 17:16:33 UTC, Tim wrote:

 Is there anything I'm doing wrong?


 You should be using a blocking socket. With them, the 
 operating system will put your thread on hold until a new 
 connection comes in. Without them, it will endlessly loop 
 doing absolutely nothing except checking if a new connection 
 is there yet. Horribly, horribly inefficient.


 Blocking sockets are now working as expected, but I've one 
 problem. When I do the following in my server-accept-thread:

 while (m_oSocket.isAlive)
 {
 	oSocketSet.reset();
 	oSocketSet.add(m_oSocket);

 	nAcceptedSockets = Socket.select(oSocketSet, null, null, 
 25.msecs);

 	if (nAcceptedSockets > 0)
 	{
 		// Do something...
 	}

 }

 ... and the following in my client:

 void connect()
 {
 	m_oSocket = new TcpSocket(AddressFamily.INET);
 	m_oSocket.connect(new InternetAddress("127.0.0.1", 12345));
 }

 The CPU usage is low as long as my connect is connected. When I 
 disconnect the client using the following few lines:

 void disconnect()
 {
 	m_oSocket.shutdown(SocketShutdown.BOTH);
 	m_oSocket.close();
 }

 ... the CPU usage goes up. I think that SocketShutdown.BOTH 
 causes Socket.select to fail which results in an endless loop. 
 Any suggestions how to handle that problem?

  Ali Çehreli: Thanks, didn't know that UFCS can also handle 
 such constructs :)


Small correction: "The CPU usage is low as long as my client is 
connected. When I disconnect the client using the following few 
lines:"
May 01 2014
prev sibling parent "Adam D. Ruppe" <destructionator gmail.com> writes:
On Thursday, 1 May 2014 at 08:08:37 UTC, Tim wrote:

 ... the CPU usage goes up. I think that SocketShutdown.BOTH 
 causes Socket.select to fail which results in an endless loop. 
 Any suggestions how to handle that problem?


It shouldn't be here, disconnect would affect the new socket, and 
you're calling select on the accepting socket, which is still 
good to accept a new connection.

What's your code look like for handing a socket returned by 
accept?
May 01 2014
prev sibling parent Justin Whear <justin economicmodeling.com> writes:
On Tue, 29 Apr 2014 17:16:32 +0000, Tim wrote:


 Hi guys,
 
 I've the following snipped:
 
 TcpSocket oSocket = new TcpSocket(AddressFamily.INET); oSocket.bind(new
 InternetAddress("127.0.0.1", 12345)); oSocket.blocking(false);
 oSocket.listen(0);
 
 while(true)
 {
 	try {
 		Socket oRequestSocket = oSocket.accept();
 
 		Request oRequest = new Request(oRequestSocket);
 		oRequest.start(); // Start request thread
 	}
 	catch (SocketAcceptException oException)
 	{
 		Thread.yield();
 	}
 }
 
 When I execute the code above, the while(true)-loop uses nearly 100% (1
 complete cpu). When I connect to the server multiple times (note that
 each Request-Thread has it's own while(oRequestSocket.isAlive)-loop) the
 cpu usage easily reaches 120, 130... 200 and more cpu usage.
 
 Is there anything I'm doing wrong? I don't want use blocking sockets...
 how to handle 100 or 1000 connections when the main server thread
 already consumes 1 cpu?


If you use blocking sockets, you should probably spawn a new thread for 
each client.  If you use non-blocking sockets, you need to use poll or 
select to wait for incoming connections or data.
Apr 29 2014