Re: debate on 700 threads vs asynchronous code

[Terje Eggestad <terje.eggestad@scali.com>]

On ons, 2003-01-29 at 18:26, Lee Chin wrote:
> Today I do method (C)... but many people seem to say that, hey,
> pthreads does almost just that with a constant memory overhead of
> remembering the stack per blocking thread... so there is no time
> difference, just that pthreads consumes slightly more memory.  That is
> the issue I am trying to get my head around.
> 
> That particular question, no one has answered... in Linux, the
> scheduler will not go around crazy trying to schedule prcosses that
> are all waiting on IO.  NOw the only time I see a degrade in threads
> would be if all are runnable.... in that case a async scheme with two
> threads would let each task run to completion, not thrashing the
> kernel.  Is that correct to say?


Yes

And you can add that if you have many runnable threads, there will be an
extra overhead doing context switching.


> ----- Original Message -----
> From: Terje Eggestad <terje.eggestad@scali.com>
> Date: 27 Jan 2003 10:48:22 +0100
> To: Lee Chin <leechin@mail.com>
> Subject: Re: debate on 700 threads vs asynchronous code
> 
> > Apart from the argument already given on other replies, you should
> > keep in mind that you probably need to give priority to doing receive.
> > THat include your clients, but if you don't you run into the risk of
> > significantly limiting your bandwidth since the send queues around your
> > system fill up. 
> > 
> > Try doing that with threads. 
> > 
> > 
> > Actually I would recommend the approach c)
> > 
> > c)  Write an asynchronous system with only 2 or three threads where I
> > manage the connections and keep the state of each connection in a data
> > structure.  
> > 
> > 
> > On fre, 2003-01-24 at 00:19, Lee Chin wrote:
> > > Hi
> > > I am discussing with a few people on different approaches to solving a scale problem I am having, and have gotten vastly different views
> > > 
> > > In a nutshell, as far as this debate is concerned, I can say I am writing a web server.
> > > 
> > > Now, to cater to 700 clients, I can
> > > a) launch 700 threads that each block on I/O to disk and to the client (in reading and writing on the socket)
> > > 
> > > OR
> > > 
> > > b) Write an asycnhrounous system with only 2 or three threads where I manage the connections and stack (via setcontext swapcontext etc), which is progromatically a little harder
> > > 
> > > Which way will yeild me better performance, considerng both approaches are implemented optimally?
> > > 
> > > Thanks
> > > Lee
> > -- 
> > _________________________________________________________________________
> > 
> > Terje Eggestad                  mailto:terje.eggestad@scali.no
> > Scali Scalable Linux Systems    http://www.scali.com
> > 
> > Olaf Helsets Vei 6              tel:    +47 22 62 89 61 (OFFICE)
> > P.O.Box 150, Oppsal                     +47 975 31 574  (MOBILE)
> > N-0619 Oslo                     fax:    +47 22 62 89 51
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> > _________________________________________________________________________
> > 
-- 
_________________________________________________________________________

Terje Eggestad                  mailto:terje.eggestad@scali.no
Scali Scalable Linux Systems    http://www.scali.com

Olaf Helsets Vei 6              tel:    +47 22 62 89 61 (OFFICE)
P.O.Box 150, Oppsal                     +47 975 31 574  (MOBILE)
N-0619 Oslo                     fax:    +47 22 62 89 51
NORWAY            
_________________________________________________________________________