From owner-freebsd-performance@FreeBSD.ORG  Wed Mar 22 18:52:42 2006
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Date: Wed, 22 Mar 2006 10:52:41 -0800 (PST)
From: Arne Woerner <arne_woerner@yahoo.com>
To: "Jin Guojun \[VFFS\]" <g_jin@lbl.gov>
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Cc: freebsd-performance@freebsd.org, oxy@field.hu
Subject: Re: packet drop with intel gigabit / marwell gigabit
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--- "Jin Guojun [VFFS]" <g_jin@lbl.gov> wrote:
> Even after your program finished, you had only 277 MB/s (DDR
memory?),
> which is far below a good motherboard. Good motherboards should
> have 500 - 900 MB/s memory bandwidth, while expensive
motherboards
> can have 1-3 GB/s memory bandwidth, which are suitable for 10
Gb/s NIC.
>
Hmm... Ok... Yes, DDR and 266FSB... So you meant, I would have
about 500MByte/sec... Then I am far below that...

My formula was: 8*277MByte/sec = 2.16...Gbit/sec -- Since dd reads
and writes memory I multiplied that with 2, which results in
4.328...Gbit/sec (50%read, 50%write) throughput... Or does a
write(2)-request to /dev/null just return without reading the
buffer? If yes, it would be just 2.16Gbit/sec for filling the
buffer with zeroes...

Then we should look again at the bandwidths in oxy's(?) setting...
I thought he just needed 500Mbit/sec alltogether (disc io, NIC
io)...

> It sounds like you have a A7V8X or similar motherboard, Do you?
>
It is an ECS K7VMM or K7VMM+ if I recall it correctly... Bought in
2003...

Is it easy to explain, why the 266FSB cannot do 8Gbit/sec without
problem? I mean: 2*133MHz*32bit=8.3125Gbit/sec... Is the MMU too
slow (e. g. due to "cheap" implementation of cache strategies) to
utilize the FSB to the maximum?

-Arne

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