Re: [Xen-devel] [PATCH v2 3/3] xl: new "loglvl" command

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Mar 15, 2016 at 01:37:39AM -0600, Jan Beulich wrote:
> >>> On 14.03.16 at 18:07, <Ian.Jackson@xxxxxxxxxxxxx> wrote:
> > Jan Beulich writes ("Re: [PATCH v2 3/3] xl: new "loglvl" command"):
> >> They could become more fine grained (for example, Linux has a
> >> few more than we have now). And the string/number correlation
> >> is an implementation detail anyway.
> > 
> > Could we solve that problem by multiplying the numbers by 10 ?
> 
> That particular one probably yes, but who knows what else
> adjustments there might be in the future. Plus - which layer
> would you see do the transformation back then? Hypervisor?
> libxc? In the end all speaks for passing around strings all the
> way down to the hypervisor then, however ugly I may
> consider such...

The constraint is that we can't delete log levels in libxl  once it is
exposed to application. If the hypervisor log level changes (especially
in case of deletion) we need to map the old one to new one. With that
in mind it make more sense to have the transformation layer in libxl.

Note that passing a string down won't give us benefit with regard to
maintaining backward compatibility -- there still needs to be a
compatibility shim somewhere in the event of deletion, so we might just
do it in libxl.

Does this make sense?

BTW I can take over the toolstack part for you if we reach agreement on
how to proceed. I think you've had enough stuff on your plate now. It
would be easier for me to write toolstack code and save both us some
time.

Wei.

> 
> Jan
> 

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