Date: Sat, 20 Oct 2001 03:41:40 +0200 From: Marko Zec <zec@tel.fer.hr> To: Mike Tancsa <mike@sentex.net> Cc: freebsd-net@freebsd.org Subject: Re: fxp driver - receive interrupt bundling Message-ID: <3BD0D653.EDC5EF8E@tel.fer.hr> References: <SEN.1003532776.274194794@news.sentex.net> <o1i1ttcg3fbn3n8n4mlv64ta9kldnmskld@4ax.com> <5.1.0.14.0.20011019211817.05a05890@192.168.0.12>
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Mike Tancsa wrote: > 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. Nice - I'd be glad if you let us know the details after you complete the experiments. Probably you could try tweaking the BUNDLE_MAX as well, if it is supported by your fxp chipset - on my cards it is not, unfortunately. If you experience high traffic volumes, than having BUNDLE_MAX restricted to only 6 frames (default) can be somewhat unnecessary limitating. Marko To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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