calling for a new workspace sizing concept - Re: auto-tune ws / headroom poc

[Dridi Boukelmoune]

On Tue, Jan 30, 2018 at 12:17 PM, Nils Goroll <slink at schokola.de> wrote:
<snip>
> * forbid any nested sizing parameters as in "if you tune knob a, you also need
>   to tune knob b" -> knob b should be replaced by a knob b' which is independent
>   of knob a and any derivation should be calculated automatically.
>
> * make workspace sizes read only parameters which users can query to estimate
>   their memory consumption
>
> * replace the workspace tunables with xxx_headroom tuning just the space
>   to remain available on the workspace after deduction of all known allocations

Hi,

Instead to new xxx_headroom knobs, why not recycle the existing workspace_xxx
parameters to take their values _in addition to_ related parameters and maybe
document it as such?

This way the description could tell that workspace_client is the space allocated
to VCL processing on the client side, and possibly (would we need to?) mention
that the total workspace size of a client transaction is "this much".

Knowing the formula would help capacity planning, so documenting it somewhere
sounds sensible all things considered.

I overall agree that we should prevent users from getting a configuration that
guarantees transactions failures.

Dridi