[K12OSN] why is printing SOOOO slow??

[Michael C Wescott]

On Wed, 2005-06-15 at 07:49, Mike Lichtenwalner wrote:
> Joe Guenther wrote:
> > One of my annoyances with K12LTSP is the extremely slow printing.  We
> > print directly to the IP address of a HP 4000 laserjet with Jet direct
> > card.  It uses CUPS v1.1.22rc1 (K12LTSP 4.2)
> > 
> > The printer waits between each page.  The CPU usage (dual 2.4Ghz Xeon)
> > goes to 100% on both CPUs when printing.  When only one job is printing,
> > one CPU will be on 100% the other lower, but with multiple docs in the
> > queue (http://127.0.0.1:631) both CPU's peak at 100% ... an the printing
> > takes a day and an age.

> We also saw that same slow performance when printing to HPLJ 4000 series 
> printers. The solution was to switch from the recommended Postscript 
> driver to the "hpijs" driver. More than 90% of our print jobs are text, 
> and the quality is good (and MUCH faster).

And one might wonder why.

CUPS is designed to give the same appearance for all printers, at least
to the extent possible. To do this it will, for many printers, convert
the document to be printed to an image. For postscript, this means
taking the postscript and interpreting it and then taking the resulting
image and rasterizing it. The resulting rasterized image is the
converted back to postscript and sent to the printer. The consequences
of all this is a lot of processing and the transformation of documents
into huge postscript images. The images are slow to transfer to the
printer (because of the size) and can be slow to be printed. But they'll
look good, even identical on different brands of printers.

If the printer is described as just a generic postscript printer CUPS
doesn't know about any peculiarities of the printer and so doesn't
bother to convert postscript (from say openoffice) to postscript of
rasterized images and everything is a lot faster. The only downside is
that you lose the ability to invoke some features of the printer like
duplex printing et al. I.e. features that may be peculiar to the type of
printer.
-- 
	Mike Wescott
	wescott at sc.rr.com