Subject: Re: upcalls?
To: Martin Husemann <>
From: Ignatios Souvatzis <>
List: tech-kern
Date: 12/09/1999 11:44:11
On Thu, Dec 09, 1999 at 10:27:56AM +0100, Martin Husemann wrote:
> > This is the absolute, complete antithesis of scheduler activations, as
> > it gives you an insane amount of overhead.  It would actually be
> > *cheaper* to just have one `kernel thread' per user thread.
> This might proove my ignorance, but I don't see the big win in having
> userland libraries fake more threads to the application than the kernel
> supports (with the one big exception beeing the kernel only supporting a
> single thread).
> Are there any results on the value of additional-userland-threads available,
> mesured in real world scenarios?

Yes. Think "networking server", for example. Something like a NNTP or HTTP
server can be coded more efficient than with fork()s, and more elegant than
single-threaded+poll()/select()+lots of legwork in the code.

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