Re: [Xen-devel] [PATCH 3 of 3] libxl: make it possible to explicitly specify default sched params

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

George Dunlap writes ("Re: [Xen-devel] [PATCH 3 of 3] libxl: make it possible 
to explicitly specify default sched params"):
>    This might be nice; but we're
> implicitly baking in an assumption that parameters with the same name
> have to have roughly similar meanings across all schedulers.

We can make this assumption true in the libxl API even if it's false
at the Xen level, simply by renaming parameters which have
"sufficiently" divergent semantics.

> Furthermore, if someone sets a "cap" in the config file, for example,
> but starts the VM in a pool running credit2, should we really just
> silently ignore it, or should we alert the user in some way?

We don't currently have any way to warn anyone about unused parameter
settings in xl config files.

> But I think whichever way we choose, we should take it to its logical
> conclusion.  Which in the "One Struct" way, would mean having a single
> domain_get/domain_set function, and in the "separate struct" way would
> probably mean specifying the scheduler -- i.e., "credit_weight",
> "credit2_weight" or something like that.  (Obviously we need xm
> compatibility, but we can throw a warning to encourage people to
> change their config files.)

Yes.

Ian.

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