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From: David Xu <davidxu@freebsd.org>
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Date: Mon, 9 Oct 2006 06:34:31 +0800
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Cc: Kip Macy <kmacy@fsmware.com>, Ivan Voras <ivoras@fer.hr>
Subject: Re: [PATCH] MAXCPU alterable in kernel config - needs testers
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On Monday 09 October 2006 04:58, Ivan Voras wrote:
> Kip Macy wrote:
> > It will only cover the single chip Niagara 2 boxes.
>
> Oh right, they'll doing multi chips in Niagara 2 :) Go Sun :)
>
> Still, single T2 chips should be more common, so I'd guess it will pay
> to optimize for that case.
>
> (For the rest of the audience: Niagara 1 has 32 logical CPUs and
> supports only one physical CPU/socket; Niagara 2 will have 64 logical
> CPUs and support > 1 CPUs/sockets; so a 2 socket Niagara 2 box will have
> 128 logical processors! Cue SciFi music...)
>
> Any word on how will they handle migration of threads across sockets (or
> will it be OS's job)? Judging from T1 architecture, I think such event
> would create a very large performance penalty, but I'm not an expert.
> __________

The current 4BSD scheduler does not handle large number of cores  very  well,
also the single sched_lock will be a bottleneck for such a configuration.