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Date:      Wed, 01 May 2002 16:15:28 -0400 (EDT)
From:      John Baldwin <jhb@FreeBSD.org>
To:        Andrew Gallatin <gallatin@cs.duke.edu>
Cc:        freebsd-smp@freebsd.org
Subject:   RE: hlt when idle?
Message-ID:  <XFMail.20020501161528.jhb@FreeBSD.org>
In-Reply-To: <15567.62317.677224.3470@grasshopper.cs.duke.edu>

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On 01-May-2002 Andrew Gallatin wrote:
> 
> 
> Can somebody remind me why we do not hlt in the idle loop on MP x86s?
> Is this because a HLTed CPU is not going to notice a new runnable job
> (possibly migrating from another CPU) until it gets an interrupt to
> wake it up?

Yes.

> Do both CPUs get clock interrupts on x86?

No, the interrupts seem to be round-robin, but each clock intr is only
sent to one CPU unlike on alpha where they are broadcast.

-- 

John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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