Date: Thu, 3 Feb 2000 12:21:14 -0700 From: "Kenneth D. Merry" <ken@kdm.org> To: Matthew Jacob <mjacob@feral.com> Cc: Thomas Stromberg <tstromberg@rtci.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: Suggestions for Gigabit cards for -CURRENT Message-ID: <20000203122114.A53673@panzer.kdm.org> In-Reply-To: <Pine.BSF.4.05.10002031034170.64395-100000@semuta.feral.com>; from mjacob@feral.com on Thu, Feb 03, 2000 at 10:50:32AM -0800 References: <20000202113259.A43505@panzer.kdm.org> <Pine.BSF.4.05.10002031034170.64395-100000@semuta.feral.com>
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On Thu, Feb 03, 2000 at 10:50:32 -0800, Matthew Jacob wrote: > > > The FreeBSD driver (written by Matt Jacob) is based on the Linux driver, > > which Intel wrote, and he hasn't yet managed to get decent throughput > > through the cards. (Maybe Matt will comment.) They also only have 64K of > > memory on board, which is insufficient for a heavily loaded server, IMO. > > That's not memory- that's FIFO- there are two of them, I believe, one for > receive, the other for xmit. You can devote 64k to ring descriptors for > receive- that's 4096 descriptors- each able to manage a 2k buffer. And > you can have two receive rings. You can have the same size for xmit. > > So, the receive performance bottleneck for this chip/board will be in how good > your PCI implementation is at first followed by how low an amount of > interrupt latency for reinstruct. If your PCI implementation can keep up with > Gigabit speeds, you're fine. If not, I'm not sure that 512K or 1MB buffering > buys you much. I think the memory would come in handy on a heavily loaded system, since you would gain a little extra time in case you were a little late servicing interrupts. i.e. it would smooth out the bumps a little bit. If your PCI implementation won't keep up with gigabit speeds, you'll just go slower. :) Most newer systems (e.g. 440BX) shouldn't have any trouble doing a reasonable amount of speed over gigabit ethernet, though. Ken -- Kenneth Merry ken@kdm.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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