Date: Sat, 29 Jun 1996 22:32:31 +1000 From: Bruce Evans <bde@zeta.org.au> To: hdalog@zipnet.net, msmith@atrad.adelaide.edu.au Cc: Kevin_Swanson@BLaCKSMITH.com, chuckr@glue.umd.edu, freebsd-hardware@FreeBSD.org, jparnas@jparnas.cybercom.net Subject: Re: muliport boards - building a PPP dialup server Message-ID: <199606291232.WAA04438@godzilla.zeta.org.au>
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>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. >I'm using my own software in a dedicated environment. I had to >look in the driver to find the "right" settings of TTY flags to >get a fast path through the driver, and I'm wondering if I'll have >to tweak things when I upgrade the OS. The data is only coming in >- nothing is going back out again. "raw" termios mode should always be fast and other line disciplines should be no slower than your line displine handler :-). The FreeBSD line discipline interface is the standard BSD per-char one so it is slower than the hacked-for-FreeBSD "raw" termios mode. This should be fixed someday. >I can't vertically scroll an Xterm with the serial mouse without >dropping input on the streaming data during a test session. If we >were to double the size of the test stand to 8 devices I'd >take a page from Henry's book and dedicate a small 486 to collect >the data and then send it to the analysis system over ethernet. There seems to be a problem with some graphics hardware or drivers disabling interrupts for too long. I get occasional overruns when switching to or from X on an S3 868 graphics card. Bruce
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