Date: Sun, 1 Feb 2004 16:53:26 -0800 From: "David O'Brien" <obrien@freebsd.org> To: Andreas Braukmann <braukmann@tse-online.de> Cc: amd64@freebsd.org Subject: Re: Dual processor, AMD 64 machine freezing. Message-ID: <20040202005326.GB60117@dragon.nuxi.com> In-Reply-To: <1071900000.1075679494@cage.int.unixxinu.de> References: <B1D77424948FD611A3B80000C0109EEF023B4D3D@SYNCRO> <1071900000.1075679494@cage.int.unixxinu.de>
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On Mon, Feb 02, 2004 at 12:51:34AM +0100, Andreas Braukmann wrote: > > P.S. For best performance, I think you really want to run 4x 512 MB. > > Running with two DIMMs means either you only get 64-bit memory access (not > > 128-bit) or else you need to put both DIMMs into the CPU1 memory slots > > (which means CPU2 will have to access those through hypertransport). > > Thats theory. ;-) > Since the allocators don't know about the numa-like architecture > memory would be accessed through hyptertransport (statistically) > more or less "half of the time". (CPU0 ---> HT ---> MEM1 ; > CPU1 ---> HT ---> MEM0) Its not theory, its fact -- even w/o a NUMA aware OS. Statistically, 1/2 the accesses by a CPU are to local memory, 1/2 to distant memory. If you put all them memory on a single CPU then you've got two processors trying to access memory, saturating the memory controller on the single CPU with memory -- thus giving you less BW. Your diagram above leaves out the memory controller (and its request buffer). -- -- David (obrien@FreeBSD.org) P.S. I work at AMD
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