Re: lkwt in DragonFly

[Miguel Mendez <flynn@xxxxxxxxxxxxxxxxxx>]

Dan Melomedman wrote:

> I hear that the main problem with Slowaris is slow fork()/exec(). So
>  Slowaris software ends-up using threads in _place_ of processes. 
> Furthermore, pthreads are a very generic threads library which is, 
> IMHO often used where it shouldn't, and also incorrectly. For 
> instance many people blindly assume that creating a bazillion threads
>  is okay because they are somehow magically faster than processes,
> but

Yes, all that is very nice but it doesn't answer my question. *Why do 
you think 1:1 doesn't work.*

> don't even bother profiling. If performance matters, than why are 
> they creating more threads than they have CPUs in the first place? 
> Also often people choose pthreads over some more convenient thread 
> library, and inflict mutexes, race conditions and other problems on 
> themselves.

Proper thread programming is not something you learn in 24h. BTDT, 
debugging threaded apps can be a real pain. I don't agree with your 
comment about having more threads that processors, though. Imagine a 
program that does some math calculations and dumps results to disk once 
in a while. You could certainly use IPC to do it, or you could run two 
threads, an i/o thread and a main thread. The i/o thread can be blocked 
on i/o while the other thread[s] keep crunching numbers, even on an UP box.

> There should not be anything inherently slow about creating a process
>  on modern OSes. If an OS has a slow fork(), that's OS designers' 
> problem, not userland programmers'.

Apples and oranges. Threaded programming has its field of application, 
regardless of whether $OS has a slow/fast fork implementation.

Cheers,
--
	Miguel Mendez <flynn@xxxxxxxxxxxxxxxxxx>
	http://www.energyhq.es.eu.org
	PGP Key: 0xDC8514F1