Number of components per init

[Norman Feske]

Hi Ben,

thanks for chiming in!

On 05.10.2016 22:22, Nobody III wrote:
> Maybe init should have an XML option
> to set its reserved RAM quota, or it could instead automatically
> calculate the required quota based on the number of components it
> starts.

The automatic calculation would work if init was solely used in a static
way. But init can actually respond to configuration changes at runtime.
Hence, the number of children may vary over the lifetime of init, which
makes it impossible to calculate the value up-front.

To address the problem in a fundamental way, init should allocate all
child-specific capabilities from the PD session of the respective child.
However, this is not a simple change. E.g., it would require us to pass
the PD session as argument to 'Entrypoint::manage' and to keep the
association of each RPC object with the PD session where its capability
was allocated from. Since this is a rare problem (actually only for init
at this point), I am not convinced to make the API more complicated for
everyone. However, I have no strong opinion yet.

In the shorter term, it would be sensible to make the preservation
configurable via init's configuration instead of hard-coding the value.
I plan to rework init soon and will keep this suggestion in mind.

> Also, it would be nice to have both reserved and maximum quotas
> for components in init's configuration.

I agree. I will consider this while reworking init.

Cheers
Norman

-- 
Dr.-Ing. Norman Feske
Genode Labs

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