--- Steve Watt <[EMAIL PROTECTED]> wrote:
> In
>
<[EMAIL PROTECTED]>,
> >N)?
>
> "Problem"? Scheduler activations may be used to
> build M:N
> systems, but that is not a requirement -- you can
> easily
> build a 1:1 (all threads are system contention
> scope) system
> with activations.
>
But the POSIX std allows one to specify that the
thread be either process scope or system scope, and if
some of them are system/process scope -that leads to
an M:N system.
> Admittedly, at this point in industry experience,
> most
> threads experts will say that M:N threading usually
> isn't
> worth the implementation headaches. But there are
Hmm -so no implementation can provide a good M:N
system.
[snip]
> convenience. Very many processes with thousands of
> threads
> in them will drag down a 1:1 system pretty rapidly.
>
I get the idea that not everyone in the pthreads-user
community is content with a 1:1 model (though I would
be).
[snip]
> handle contention scope correctly. I don't think
> anyone
> has built such a system, but would be happy to be
> proven
> wrong -- it'd be a useful advancement of the art.
Isn't a system supporting both process/system scope a
POSIX requirement?
BTW -the std sounds weird to me at times. They want to
treat a process as a shell with a single
(hypothetical) thread in it -and their scheduling
classes don't have a 1:1 correspondence to the unix
scheduler. SCHED_RR is a realtime scheduling class but
I mistook it for a round robin scheduler:-).
> One
> challenge is accounting for time on threads that
> don't do
> much work when awakened before going back to sleep
If every kernel thread were to be treated at par with
a process, we wouldn't need a special algorithm.
regards
-kamal
------------------------------------------------------------
Kamal R. Prasad
UNIX systems consultant
[EMAIL PROTECTED]
In theory, there is no difference between theory and practice. In practice,
there is:-).
------------------------------------------------------------
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