[BlueOnyx:26993] Re: Error changing settings on Aventurin{e} CT

[Colin Jack]

Hi Michael,

> I tried changing the CPU units on one of my CTs on 6109R Aventurine and
> when I save it throws big red errors for numiptent_l and numproc_l
> although I haven’t changed those.

Yeah, the saving of the parameters sometimes goes off the rails. This is
due to the way how they are calculated may not coincide with maximums
that are actually allowed due to hardware limitations.

To make sure that one or two of such glitches don't interfere with
saving changes they various parameters are saved individually or in
small groups, so that most changes still go through even if there is an
error in one or two subsidiary parameters.

"numpitent" is the limit for individual firewall rules.
"numproc" is the limit for the amount of processes a CT might have.

2K firewall rules might be to small or too big. Hard to say.
131K processes sure is big.

But here is the thing: These are probably set to "unlimited" anyway. In
the past in older OpenVZ versions you HAD to configure every bloody
parameter to at least some value and that often then went off the rails.
Even the OpenVZ guys eventually realized that this was overkill and
allowed many of the more nonsensical parameters to be set to unlimited.
Or have them default to unlimited when they aren't configured
explicitly. But even there: There is no value "unlimited" that you can
use. As far as the config files go it's still a number and how big that
number is depends on your hardware specs. Which makes it totally
unintuitive and even more complicated to set it correctly.

 > I think this may have something to do with the settings having
 > Unlimited (with a capital U) rather than unlimited (lower case)

Yes and no. The code handles both "Unlimited" and "unlimited" and then
tries to determine what the maximum number that's allowed might be and
tries to set that. And that "guess" is probably wrong for both
parameters. Either way: You can ignore "numiptent" and "numproc", as the
way they are configured now is as close to unlimited as it might get on
your end of things.

 > Looking at the vz conf file for the CT it seems to have applied the
 > increased cpuunits but the settings for physpages and swappages don’t
 > seem right (should be 8G and 4G)?

The values for RAM and Swap are stored in pages, not gigabytes. There
also isn't a singular parameter for RAM, as that is broken down into
various subtypes.

You can try to set 8GB RAM and 2GB swap from the command line like this:

prlctl set <VPSID> --memsize 8GB --swap 2GB

That will set and write out the correct limits for memory and swap. It
will break it down automatically to create the correct settings for the
associated memory related parameters such as physpages, lockedpages,
shmpages, privvmpages and vmguarpages.

Thanks – that all makes sense.
I will ignore the errors. :0)

All the best

Colin
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