On Tue, 25 Jan 2005 04:20:56 +0100, Mario Hoerich <[EMAIL PROTECTED]> wrote:
> # Gert Cuykens:
> > can somebody explain what the difference is between forks and
> > threads
>
> Nutshell version: fork(2) produces a new process, which may consist
> of multiple threads.
>
> fork(2)ing used to be slightly more expensive, as it creates a new
> process with an accompanying process control block (PCB) and
> allocates its own memory pages. Threads just use their processes'
> data segment and thus share pages. Which basically means one thread
> can trash another's data, whereas related processes can not.
>
> OTOH the time slices handed out by the process scheduler
> ("Hey! PID 384! Your turn for the next 20ms!") are further subdivided
> by the thread scheduler. Since both thread scheduler and context
> switches between threads produce some overhead (storing local data,
> instruction pointer and such) threads used to reduce the real CPU
> time a process could actually use for its algorithms.
>
> I said "used to", because this is basically the theory introductory
> textbooks on OS design will tell you.[1] There's plenty of ways to
> adapt costs, i.e. by making the process scheduler hand out larger
> slices to multithreaded processes or employing copy-on-write, which
> means that the parent processes' pages are just mapped into the child
> process, until the child actually writes to them. Traditionally,
> Unices had pretty cheap processes but rather expensive threads.
> (Windows, for example, had it the other way around).
>
> I didn't delve into this for quite a while, so sadly, I can't give
> you any details on the current state of things.
>
> HTH,
> Mario
>
> [1]:
> Be warned, this is from the top of my head and it's 4am in the
> morning with my bed waiting for me. I just hope I've been at
> least *somewhat* coherent... ;)
>
thx ps can you tell me who is winning at the moment ? The fork or the spoon ?
bsd 6 is still a fork right ?
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