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Date:      Sun, 28 Nov 1999 16:00:42 -0800 (PST)
From:      Julian Elischer <julian@whistle.com>
To:        peter.jeremy@alcatel.com.au
Cc:        freebsd-arch@freebsd.org
Subject:   Re: Which is the truth? (sycalls and traps)  (fwd)
Message-ID:  <Pine.BSF.4.10.9911281554080.544-100000@current1.whistle.com>
In-Reply-To: <99Nov29.103530est.40344@border.alcanet.com.au>

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On Mon, 29 Nov 1999, Peter Jeremy wrote:

> On 1999-Nov-29 09:28:00 +1100, Julian Elischer wrote:
> >(If the UTS is running then we just block the entire process)
> 
> This could easily become a bottleneck on a large SMP system.  I don't
> believe the kernel scheduler should need to obtain an SMP lock for its
> entire execution.  Requiring this for a UTS sounds like a performance
> hit.
> 

If the Scheduler itself had a pagefault, the last thing you want to do is
make an upcall to the scheduler!
Since the schedular is constantly active this would probably only happen
during startup. Though in scheduling a long asleep thread, it's stack may
be out on swap. You'd need to work out a way of 'pre-faulting' in the
thread's context so that the scheduler didn't block trying to load it.
or at least scheduling it in a way that allowed the fault to not be 
charged against the scheduler, but rather against the thread.

The second may actually not be too hard.

Julian


> Peter

> 





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