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From: David Xu <davidxu@freebsd.org>
To: Bruce Evans <bde@zeta.org.au>
Date: Thu, 23 Nov 2006 15:09:08 +0800
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Subject: Re: superpage plans
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On Thursday 23 November 2006 14:53, David Xu wrote:
> Do you really believe IPI_PREEMPTION works as expected ? the problem
> is in sched_4bsd.c, the remote cpu running an idle cpu is only
> interrupted by IPI_AST not IPI_PREEMPT, IPI_AST has no effect for kernel
> thread, note that kick_other_cpu is only used for bound thread which is
> being resumed, kick_other_cpu does send IPI_PREEMPT,  though pagezero
> thread is a bound thread in most time, but it is not the case that
> kick_other_cpu will be used, we want to preempt it not resuem it, so
> PREEMPTION and IPI_PREEPMTION do not work for pagezero thread running
> on remote cpu.
>
> David Xu
the above may not be very clear.  The forward_wakeup only selects idle
cpu,  so a thread is being added will not preempt remote cpu which is
running pagezero thread.