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Date:      Sun, 14 Sep 1997 13:03:59 -0700 (PDT)
From:      Simon Shapiro <Shimon@i-connect.net>
To:        Terry Lambert <tlambert@primenet.com>
Cc:        missmanp@milo.cfw.com, freebsd-smp@freebsd.org
Subject:   Re: SMP in FreeBSD 3.x.x
Message-ID:  <XFMail.970914130359.Shimon@i-Connect.Net>
In-Reply-To: <199709140955.CAA14249@usr06.primenet.com>

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Hi Terry Lambert;  On 14-Sep-97 you wrote: 
> > When I worked at that awful place, we actually computed how many
> > processors
> > one could put on the P6 bus.  The number was much, much lower than 30.
> > Our number was based on trying to have the CPUs access memory and I/O.
> > 
>  With respect, that's because the people designing the access paradigms
>  weren't very clever.  It's possible to allocate from a global pool
>  to a per processor pool.
>  
>  If I'm trying to allocate out of a per processor pool, then I
>  don't have to contend with other processors to do the allocation.
>  
>  In effect, this is a virtual NUMA.
>  
>  See the Dynix paper:
>  
>       Efficient Kernel Memory Allocation on Shared Memory Multiprocessors
>       McKenney, P.E. and Swignline , J.
>       Proceeding of Winter 1993 Usenix Technical Conference
>       Jan 1993, pages 295-303

The Dynix papers were used as a model to scale SMP vs. MPP.  The concusion
(in another job, the awful place did not know their head from their tail
:-) was that aroud 30 processors is where scalability will fall off.  We
used Dynix + Oracle for O/S application model.  Processor was Pentium.  If
I remember correctly, the P6-200 has worse instructions/memory/IO bandwidth
ratios than Pentiums-66 does.  That led to the conclusion that we will not
grow beyond 30 either.  I will not go into what the initial P7 was supposed
to do.  I have no clue where it ended being.

---


Sincerely Yours,                               (Sent on 14-Sep-97, 12:58:09
by XF-Mail)

Simon Shapiro                                                Atlas Telecom
Senior Architect         14355 SW Allen Blvd., Suite 130 Beaverton OR 97005
Shimon@i-Connect.Net          Voice:  503.643.5559, Emergency: 503.799.2313



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