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Date: Wed, 10 Aug 2005 06:06:37 -0700 (PDT)
From: Bsderss <snort_sam@yahoo.com>
To: Robert Watson <rwatson@FreeBSD.org>,
	Momtchil Momtchev <momtchil.momtchev@netasq.com>
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Cc: freebsd-current@freebsd.org, Bsderss <snort_sam@yahoo.com>
Subject: Re: RTCoreBSD
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--- Robert Watson <rwatson@FreeBSD.org> wrote:

> 
> On Wed, 10 Aug 2005, Momtchil Momtchev wrote:
> 
> > No, kqueue/kevent is not realtime, as the whole
> FreeBSD kernel doesn't 
> > support hard real-time scheduling. In order to
> have hard real-time 
> > scheduling you should have a fully preemtible
> kernel, which schedules 
> > and preempts everything (even interrupt handlers).
> The RTCoreBSD uses a 
> > two-kernel approach with a real-time microkernel
> which runs the FreeBSD 
> > kernel as a process, providing a virtual interrupt
> controller. The 
> > real-time processes run directly on the
> microkernel and can't directly 
> > use the FreeBSD kernel services.
> 
> While FreeBSD is not a hard realtime system, it does
> have increasing 
> propertis of one: FreeBSD 6.0 ships with kernel
> preemption enabled by 
> default, and the priority propagation and priority
> management in the SMPng 
> locking primitives moves in that direction also. 
> FreeBSD will preempt one 
> running ithread with one associated with a new
> interrupt if the scheduler 
> decides that's appropriate based on their
> priorities.  With Giant off most 
> of the kernel, a lot of problems with deferred
> processing due to large 
> lock size have gone away.
> 
What will be this affect to our multi-threaded and
multiplex programming?

Sam
> Robert N M Watson
> _______________________________________________



		
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