The other thing to check for is that you are not putting 32bit or 33Mhz cards in
the 64bit/66Mhz slots. This will force down the overall speed down the slowest
device.. And also reduce the bus speed between the north and south chipsets
(depending of course on what chipset you are using).
On Fri, 11 Oct 2002 17:24:42 -0700
Terry Lambert <tlambert2@mindspring.com> wrote:
> Cheng Jin wrote:
> > > It may be your SysKonnect card. It's very easy to get full wire
> > > speed with 1500 MTU packets on an 800MHz machine with Tigon III
> > > cards (for example). It's all in the tuning.
> >
> > Sorry, I didn't make myself clear in my previous message. We were able to
> > get 1 Gbps when we pump data through one SysKonnect card (SMP or not).
> > The problem is when we try to use both cards under FreeBSD SMP kernel, the
> > throughput on each card is only 640 Mbps. In fact, using a
> > single-processor kernel, we could get 560 Mbps going through both cards.
> >
> > The cards seem fine, the problem seems to be with the SMP kernel.
>
> FreeBSD never routes interrupts to more than a single processor
> at a time. I believe Linux does the same, though it does not
> select the CPU to target the same way. NT assigns cards to CPUs
> to distribute the load.
>
> As things currently stand, you should always get better overall
> numbers on tests like this with a UP FreeBSD system, unless you
> are willing to take suggestions on your test configuration.
>
> 33Mhz x 32 bits ~= 1.32Gbit burst rate; this could be a PCI bus
> limitation.
>
> You didn't say how fast your PCI bus was, whether you were using
> 64 bit slots for each card, whether they were/were not sharing a
> PCI interrupt with other cards, etc..
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