On 31/05/2019 17:52, Dario Faggioli wrote:
> On Tue, 2019-05-28 at 12:33 +0200, Juergen Gross wrote:
>> Instead of having a full blown scheduler running for the free cpus
>> add a very minimalistic scheduler for that purpose only ever
>> scheduling
>> the related idle vcpu. This has the big advantage of not needing any
>> per-cpu, per-domain or per-scheduling unit data for free cpus and in
>> turn simplifying moving cpus to and from cpupools a lot.
>>
>> As this new scheduler is not user selectable don't register it as an
>> official scheduler, but just include it in schedule.c.
>>
>> Signed-off-by: Juergen Gross <jgr...@suse.com>
>> ---
>> V1: new patch
>> ---
>
>> --- a/xen/common/schedule.c
>> +++ b/xen/common/schedule.c
>> @@ -83,6 +83,57 @@ extern const struct scheduler
>> *__start_schedulers_array[], *__end_schedulers_arr
>>
>> static struct scheduler __read_mostly ops;
>>
>> [...]
>>
>> +static void *
>> +sched_idle_alloc_vdata(const struct scheduler *ops, struct
>> sched_unit *unit,
>> + void *dd)
>> +{
>> + /* Any non-NULL pointer is fine here. */
>> + return (void *)1UL;
>> +}
>> +
> I think the proper thing to do, here, would be to convert alloc_vdata()
> to PTR_ERR() & IS_ERR().
>
> That's another patch, of course, and given that this series is rather
> big already, I'm not sure about asking for it to be done in the context
> of this work.
>
> I can do it myself, either right now or after this series is merged
> (for the sake of not making rebasing 60 patches more complicated than
> it must be already, for you :-D).
>
> Let me know what you think.
There is only one place left where alloc_vdata is being called for the
idle scheduler, and that is sched_init_vcpu() of an idle vcpu.
I have planned to do a followup series cleaning up the scheduling stuff
where I can add a patch special casing that and removing
sched_idle_alloc_vdata().
Juergen
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