Re: [Xen-devel] [PATCH] xen: Credit2: enable fully custom runqueue arrangement

[Dario Faggioli <dfaggioli@xxxxxxxx>]

On Wed, 2018-01-24 at 11:44 +0000, George Dunlap wrote:
> On 09/13/2017 05:21 PM, Dario Faggioli wrote:
> > diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-
> > command-line.markdown
> > index 9797c8d..dbf5d4c 100644
> > --- a/docs/misc/xen-command-line.markdown
> > +++ b/docs/misc/xen-command-line.markdown
> > @@ -585,6 +585,16 @@ Available alternatives, with their meaning,
> > are:
> >  * `node`: one runqueue per each NUMA node of the host;
> >  * `all`: just one runqueue shared by all the logical pCPUs of
> >           the host
> > +* `<custom>`: one runqueue per each specified subset of logical
> > +              pCPUs of the host. Subsets are defined either as:
> > +              `[[0,1,][2,6][3,5][4,7]]`, or as:
> 
> Is the comma after the 1 there a typo, or do are you explicitly
> trying
> to communicate that you tolerate terminal commas?
> 
The former. A typo. :-)

> > +
> > +        /* Is the cpu ID we found valid? */
> > +        if ( cpu >= nr_cpu_ids )
> > +            return false;
> > +
> > +        /*
> > +         * CPU IDs are considered only the first time they're
> > found in the
> > +         * string considere. Multiple subsequent occurrences are
> > ignored.
> > +         */
> > +        if ( cpumask_test_cpu(cpu, &cpus) )
> > +            continue;
> > +
> > +        cpumask_set_cpu(cpu, &cpus);
> > +        custom_cpu_runqueue[cpu] = rqi;
> > +    }
> > +
> > +    /*
> > +     * If in_subset is true, it means we are in format 1, and we
> > +     * found a subset that was not closed with its ']', which
> > +     * means the string is malformed.
> > +     */
> > +    if ( in_subset )
> > +        return false;
> > +
> > +    return ret;
> > +}
> 
> Rather than nitpick the state machine here, I wonder if we could add
> some unit tests to make sure that the parser continues to be have as
> expected.  We could either do some trickery to allow it to run in
> user
> mode (as the x86_emulate() harness); or we could run some tests
> during
> boot-up when running in DEBUG mode.
> 
I like the idea. Not sure which one of the two options I'd prefer...
Probably the "run in usermode" one, if it's not too complicated (I'll
have a look).

> If you can't pick this up, I can probably make time to do it.
> 
I think I can take care of this.

Thanks and Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Software Engineer @ SUSE https://www.suse.com/

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