Re: [Xen-devel] [PATCH v2 07/10] xen: credit2: always mark a tickled pCPU as... tickled!

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Thu, Feb 9, 2017 at 11:48 PM, Dario Faggioli
<dario.faggioli@xxxxxxxxxx> wrote:
> On Thu, 2017-02-09 at 14:59 +0100, Dario Faggioli wrote:
>> In fact, whether or not a pCPU has been tickled, and is
>> therefore about to re-schedule, is something we look at
>> and base decisions on in various places.
>>
>> So, let's make sure that we do that basing on accurate
>> information.
>>
>> While there, also tweak a little bit smt_idle_mask_clear()
>> (used for implementing SMT support), so that it only alter
>> the relevant cpumask when there is the actual need for this.
>> (This is only for reduced overhead, behavior remains the
>> same).
>>
> So, while working on other things with this series applied, I noticed
> some strange behavior, for which it turned out this patch is
> responsible.
>
> More specifically...
>
>> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
>> index addee7b..bfb4891 100644
>> @@ -1289,9 +1300,8 @@ runq_tickle(const struct scheduler *ops, struct
>> csched2_vcpu *new, s_time_t now)
>>                      sizeof(d),
>>                      (unsigned char *)&d);
>>      }
>> -    __cpumask_set_cpu(ipid, &rqd->tickled);
>> -    smt_idle_mask_clear(ipid, &rqd->smt_idle);
>> -    cpu_raise_softirq(ipid, SCHEDULE_SOFTIRQ);
>> +
>> +    tickle_cpu(cpu, rqd);
>>
> ... this, quite obviously, wants to be:
>
>   tickle_cpu(ipid, rqd);
>
> I'll fix this in v2.

You mean v3? :-)

You can add:

Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>

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