FOUNDIT (was Re: massive threading performance)

[Paul Sijben]

I found that the problem was caused by the sending thread not giving
control back quickly enough to the receiving thread.

Also in going through the code I found an old self.s.setblocking(0)call
that was no longer relevant. Removing that solved my problem.

Something that took 20 seconds now takes just 1.

Thanks to those who took the time to respond to my earlier messages.

Paul

Paul Sijben wrote:
> OK the problem I posted about earlier is NOT a UDP/socket problem, it is
> a threading problem. Albeit one that only happens when you have many
> thrreads????
> 
> I have made two little scripts using the code I copied below, one client
> and one server (attached).
> 
> If I run them concurrently on the same machine I see the following times:
>>> 1145526192.825508
> <<1145526192.825848
> 
>>> 1145526193.829325
> <<1145526193.834927
> 
> a transfer time in the milliseconds. Much less than the times I see in
> the full application.
> 
> OK so I put them both in a multithreaded script (also attached)
> 
> 
>>> 1145526971.619558
> <<1145526971.619909
> 
>>> 1145526972.619241
> <<1145526972.619647
> 
> again transfer time in milliseconds.
> 
> Not like this that I get from the profile of my code:
> << 1145517554.363850 send
>>> 1145517554.647485 recv
> 
> which uses the same communication and threading but has 20+ threads?
> 
> Now I am completely baffled!
> 
> again I really appreciate if anyone can shed light on this!
> 
> Paul
> 
> 
> Paul Sijben wrote:
>> I am stumped by the following problem. I have a large multi-threaded
>> server accepting communications on one UDP port (chosen for its supposed
>> speed).
>>
>> I have been profiling the code and found that the UDP communication is
>> my biggest drain on performance! Communication where the client and the
>> server are on the same machine still takes 300ms or sometimes much more
>> per packet on an Athlon64 3000+ running Linux (Fedora Core 5 x64).
>>
>> I must be doing something wrong and would really appreciate feedback on
>> my code below:
>>
>> I open the server port with
>>
>> 	self.s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
>> 	self.s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
>> 	self.s.bind((myaddress, myport))
>>
>> I then open a client port with
>>
>> 	self.s=socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
>> 	self.s.connect((host, port))
>>
>> the client sends data with
>>
>> 	self.s.sendall(data)
>>
>> and the server with
>>
>> 	self.s.sendto(data,link.remoteaddress)
>>
>> both receive with
>>
>> buf, address = socket.recvfrom(8192)
>>
>> The sender and receiver are in separate threads (threading.Thread).
>>
>> Does anyone know what is going wrong here, the socket communication, the
>> thread scheduling?
>>
>> Paul Sijben
>>
> 
> 
> 
> ------------------------------------------------------------------------
> 
> import socket
> import time
> 
> profile=[]
> 
> s=socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
> s.connect(('127.0.0.1', 42420))
> print ">>%f"%time.time()
> s.sendall('testerdetest')
> time.sleep(1)
> print ">>%f"%time.time()
> s.sendall('testerdetest')
> print ">>%f"%time.time()
> 
> 
> 
> ------------------------------------------------------------------------
> 
> import socket
> import time
> 
> profile=[]
> 
> 
> s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
> s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
> s.bind(('', 42420))
> 
> 
> buf, address =s.recvfrom(8192)
> print "<<%f"%time.time()
> print buf, address
> buf, address =s.recvfrom(8192)
> print "<<%f"%time.time()
> print buf, address
> 
> 
> ------------------------------------------------------------------------
> 
> import socket
> import time
> import threading
> profile=[]
> 
> class server(threading.Thread):
> 	def __init__(self):
> 		self.s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
> 		self.s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
> 		self.s.bind(('', 42420))
> 		threading.Thread.__init__(self)
> 		self.start()
> 		
> 	def run(self):
> 		buf, address =self.s.recvfrom(8192)
> 		print "<<%f"%time.time()
> 		print buf, address
> 		buf, address =self.s.recvfrom(8192)
> 		print "<<%f"%time.time()
> 		print buf, address
> 		
> class client(threading.Thread):
> 	def __init__(self):
> 		self.s =socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
> 		self.s.connect(('127.0.0.1', 42420))
> 		threading.Thread.__init__(self)
> 		self.start()
> 		
> 	def run(self):
> 		print ">>%f"%time.time()
> 		self.s.sendall('testerdetest')
> 		time.sleep(1)
> 		print ">>%f"%time.time()
> 		self.s.sendall('testerdetest')
> 		print ">>%f"%time.time()
> 	
> 
> serv=server()
> cl=client()