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Date:      Thu, 22 Jun 1995 17:15:17 +0200
From:      Julian Howard Stacey <jhs@vector.eikon.e-technik.tu-muenchen.de>
To:        current@freebsd.org
Subject:   kernel response
Message-ID:  <199506221515.RAA00867@vector.eikon.e-technik.tu-muenchen.de>

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This is mainly for our Kernel & Parallel Port Driver people
	(David, & Geoff Rehmet ? )

When I print via the standard spooler (lpr -#2), a 300K file, going to an hp3p
laser via a parallel port, all screen updating goes dead for several seconds,
( the -#2 doubles the data, doesnt use the PCL5 print twice escape sequence).

My config is:
	X11R6pl11+XFree86_3.1.1
	33MHz 486, 16M RAM, FreeBSD current,
	swapinfo:
		swapinfo
	Device      1K-blocks     Used    Avail Capacity  Type
	/dev/sd0s2b     32768    11456    21248    35%    Interleaved
	/dev/sd2s3b     32768    11440    21264    35%    Interleaved

	kernel conf:
		device  lpt0    at isa? port 0x378 tty irq 7 vector lptintr
		device  lpt1    at isa? port 0x278 tty
	(only lpt0 connected)

dmesg reports
	lpt0 at 0x378-0x37f irq 7 on isa
	lpt0: Interrupt-driven port
	lp0: TCP/IP capable interface
	lpt1 at 0x278-0x27f on isa

All other task were quiescent, there was no serial or ether traffic
(other ether device powered off, so no broadcast stuff either)
I had X running, 2 ghostviews, 6 xterms (all quiescent)
no crontab driven system resource leaching stuff, & all my hard drives
were quiescent.

The keystrokes I typed while the OS went signle mindedly about flushing its
file to laser were latched, & my vi in xterm did finally respond to go up
screen 4 lines (without screen roll, so not even a screen redraw needed),
but the response was abysmal (reminded me of the bad old days of inbuilt
print software under Wordstar ;-)

The laser has 4M of extension RAM, so it wasnt overflow causing weird errors,
The data was a .pcl file previously produced by Ghostscript from a .ps
(I dont have a Postscript cartridge in my laser, I guess if one did, it might
stop FreeBSD flow periodically, to process data, thus giving FreeBSD a
chance to to service other requests, but I have nothing to stop the full
600K of data being sent to the parallel port).

So it seems the parallel port output flush is running at too high a priority
for too long.

If I've forgotten to mention something, please let me know.

--	--	--	--	--	--	--	--	--	--
Julian Stacey
Recommended <JHS@FreeBSD.Org>,  Alternate <jhs@regent.e-technik.tu-muenchen.de>
Localhost 	<jhs@vector.eikon.e-technik.tu-muenchen.de>



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