Date: Fri, 19 Oct 2001 21:19:54 -0400 From: Mike Tancsa <mike@sentex.net> To: Marko Zec <zec@tel.fer.hr> Cc: freebsd-net@freebsd.org Subject: Re: fxp driver - receive interrupt bundling Message-ID: <5.1.0.14.0.20011019211817.05a05890@192.168.0.12> In-Reply-To: <3BD0D063.C084B21D@tel.fer.hr> References: <SEN.1003532776.274194794@news.sentex.net> <o1i1ttcg3fbn3n8n4mlv64ta9kldnmskld@4ax.com>
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At 03:16 AM 10/20/2001 +0200, Marko Zec wrote:
>It doesn't matter how many fxp cards you have installed - if your box acts
>as a
>server than most probably you can leave INT_DELAY at default value (Intel
>proposes 0x600, but I think 0x400 would be more appropriate).
>
>If you use your multi-fxp-card BSD box as a router, than the microcode will
>impose additional delay *twice* (once in each direction), so in that case the
>default value of 0x600 might be too high for achieving full 100 megE
>throughput, because of TCP windowing scheme having to wait for ACK frames,
>which will be held in fxp receive buffers too long. On the other hand, setting
>INT_DELAY too low minimizes the benefits of bundling interrupts, as fewer
>received frames get "bundled" on a single interrupt.
>
>To summarize: if you are doing any routing (or bridging as I do), find the
>best
>value for INT_DELAY for your specific environment experimentally, it should be
>definitely smaller than or equal to 0x400. If you don't do packet forwarding
>between fxp interfaces, use the defaults.
Thanks! This is for a router pushing upwards of 20Mb/s with about 110K
routes on 4 interfaces. I will try and experiment a bit on my test setup
first to see what works best.
---Mike
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Mike Tancsa, tel +1 519 651 3400
Sentex Communications, mike@sentex.net
Providing Internet since 1994 www.sentex.net
Cambridge, Ontario Canada www.sentex.net/mike
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