Date: Sat, 29 Jun 1996 10:37:56 -0400 (EDT) From: Chuck Robey <chuckr@Glue.umd.edu> To: Bruce Evans <bde@zeta.org.au> Cc: freebsd-hardware@FreeBSD.org Subject: Re: muliport boards - building a PPP dialup server Message-ID: <Pine.OSF.3.91.960629103348.5294D-100000@modem.eng.umd.edu> In-Reply-To: <199606291232.WAA04438@godzilla.zeta.org.au>
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[CC: list trimmed, these guys are all on hackers anyways] On Sat, 29 Jun 1996, Bruce Evans wrote: > >As you know once you're in the interrupt routine it will > >check all ports, meaning that in the special case of input streaming > >in on multiple ports you will have a big reduction in interrupt load. > >I second looking up some of Bruce's postings. > > This is actually the weakest point in the sio driver. Polling 16 > ports wastes a lot of time when only a few of them are active, and > I think processing multiple ports per interrupt is relatively rare > even when many of them are active. The poll is only for interrupt- > pending, not for input-available so it only finds input when the > the fifo is full. Are you sure of that, Bruce? I spoke a long while back with a guy who'd written the digiboard driver for sysV machines, and he claimed that, except when only one port was active, that it was actually much more efficient to ignore which uart had actually issued the interrupt, and simply service them all on each interrupt. He said he'd done some testing to back that up, altho I don't have the specifics anymore (this was at least 5 years ago). ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@eng.umd.edu | communications topic, C programming, and Unix. 9120 Edmonston Ct #302 | Greenbelt, MD 20770 | I run Journey2 and n3lxx, both FreeBSD (301) 220-2114 | version 2.2 current -- and great FUN! ----------------------------+-----------------------------------------------
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