Date: 17 Jul 1996 20:29:19 +0200 From: "Stefan Bethke" <stefan@Promo.DE> To: "Dennis" <dennis@etinc.com> Cc: hackers@freebsd.org Subject: Re: mitsumi CD-ROM Message-ID: <n1374487071.58218@quick.Promo.DE>
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> stealing the bus is stealing the cpu when a router is doing largely > transfers from cards. Your cant process packets until you get them. And = if > the cpu is in a transfer cycle and cant get the bus then its idle. > > I dont want my packet transfers being interrupted by trivial disk = activity. > An IDE will only use the CPU when it has it already anyway.....a > bus-master makes the system much less predictable and assumes the wrong > priorities. The priorities are independent of whether programmed IO or bus-mastering = is used; if a disk controller has the higher priority, it will interrupt = a network controller regardless. If I understand you correctly, you want the disk controller only to = consume resources when there is no network activity; I'm not too familiar = with PCI's or FBSD's arbitration logic, but I assume that FBSD will try = to service disk controllers before network controllers (please correct me = on this). I'm sure one could change that with some effort to give the nic = the higher priority. However, if you're intention is to really make this one router forward = packets with lower latency, you might want to try to run it completely = off MFS; then there will be no disk activity at all. Stefan
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