Date: Sun, 9 Mar 1997 23:54:11 +0100 From: j@uriah.heep.sax.de (J Wunsch) To: hackers@FreeBSD.ORG Cc: bmcgover@cisco.com (Brian McGovern) Subject: Re: Performance questions (Interrupt vs. polled) Message-ID: <19970309235411.LH28573@uriah.heep.sax.de> In-Reply-To: <3.0.32.19970307084514.00905c60@visigenic.com>; from Tim Oneil on Mar 7, 1997 08:45:15 -0800 References: <3.0.32.19970307084514.00905c60@visigenic.com>
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As Tim Oneil wrote: > No flame. My learned opinion however is that a system with efficiant thread > scheduling (such as freeBSD) is best served by polling. Interrupted tasking > is best for serial, brain-dead systems, like DOS. You've just got this reversed. A decent multiprocessing system benefits a lot from hardware that can do interrupt notification right when there is something to do. The worst that could happen are CPU spin loops where the CPU is waiting for some bit to be set by a peripheral device. (That's why IDE drives are ugly.) To the contrary, DOS often doesn't use interrupt-controlled drivers, so you can even work with peripherals that have a broken-by-design interrupt behaviour (like the IRQ clash for COM1/3 or COM2/4). This doesn't do much harm there, since it's a single-process system, so the CPU has to wait anyway until the current operation has completed. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)
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