dlu@wobble.UUCP (Doug Urner) (11/07/88)
I'm looking for information on measuring tty sub-system performance. Pointers to articles and/or benchmarks, anecdotes and insight into the issues involved would all be appreciated. Doug Urner uunet!wobble!dlu 206/676-5759
jfh@rpp386.Dallas.TX.US (John F. Haugh II) (11/09/88)
In article <138@wobble.UUCP> dlu@wobble.UUCP (Doug Urner) writes: >I'm looking for information on measuring tty sub-system performance. >Pointers to articles and/or benchmarks, anecdotes and insight into the >issues involved would all be appreciated. Once I was charged with testing the I/O performance on a certain vendor's 68000 system. The tty sub-system was controlled by a 12MHz 68000 running without interrupts polling a collection of dual UARTS. My test was to copy a single character from one port to the next, and back, counting the number of characters per second. The ports were set for 38.4KBaud, so I expected several hundred characters per second ... The result was < 50 cps. Turns out the polling was driven by a 10ms clock. Every 10ms all the UARTS were checked for incoming characters, so the process would invariably sleep for at least 10ms waiting on the character it had just now been sent by the producing process. Or something like that. Moral: When testing tty systems, always try at least one perverse case. -- John F. Haugh II +----Make believe quote of the week---- VoiceNet: (214) 250-3311 Data: -6272 | Nancy Reagan on Artifical Trish: InterNet: jfh@rpp386.Dallas.TX.US | "Just say `No, Honey'" UucpNet : <backbone>!killer!rpp386!jfh +--------------------------------------