[cups.general] Sense and nonsense of RIPCache

[Michael Sweet]

On Jul 27, 2010, at 3:40 AM, Till Kamppeter wrote:
> ...
> What is the RIPCache important for?

It is important for large print servers that need to limit the amount of memory used by RIP filters.  8MB is not much for a typical desktop PC these days, but Ghostscript shouldn't fail like it is doing (and never used to...)

Similarly, we provide FilterLimit and FilterNice controls so that administrators can tune the performance of the printing system appropriately.

> Why do we default it to 8MB?

At the time CUPS was first written (1997ish), 8MB was a significant portion of memory for the systems we ran it on (where 128MB of system RAM was common).  These days desktop systems often have 2GB or more, however popular ARM-based file/print servers still only have 512MB or less of memory and so I would be opposed to a higher default absolute value.

> Why don't we let Ghostscript and imagetoraster determine the available 
> memory automatically?

Because a) you are putting a lot of burden on each RIP filter to make that kind of guess and b) whatever guess we use will likely be wrong since the filter doesn't know what your real workload is.

> Or should we better default to automatic setting 
> by the filters if the RIPCache in cupsd.conf is not set (simply let CUPS 
> not set the environment variable RIP_MAX_CACHE if RIPCache is not set)?


I think it is entirely appropriate for cupsd to set a default value for the filters (one place to configure things...), and we could add a "percent" unit that would be converted to an absolute value based on physical memory.

________________________________________________________________________
Michael Sweet, Senior Printing System Engineer, PWG Chair




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