Re: [PATCH 09/10] x86/intel_rdt: Hot cpu support for Cache Allocation

[Vikas Shivappa]

On Wed, 24 Jun 2015, Thomas Gleixner wrote:

> On Tue, 23 Jun 2015, Vikas Shivappa wrote:
> > +/*
> > + * cbm_update_msrs() - Updates all the existing IA32_L3_MASK_n MSRs
> > + * which are one per CLOSid except IA32_L3_MASK_0 on the current package.
> > + */
> > +static inline void cbm_update_msrs(void)
> > +{
> > +	int maxid = boot_cpu_data.x86_cache_max_closid;
> > +	unsigned int i;
> > +
> > +	/*
> > +	 * At cpureset, all bits of IA32_L3_MASK_n are set.
> > +	 * The index starts from one as there is no need
> > +	 * to update IA32_L3_MASK_0 as it belongs to root cgroup
> > +	 * whose cache mask is all 1s always.
> > +	 */
> > +	for (i = 1; i < maxid; i++) {
> > +		if (ccmap[i].clos_refcnt)
> > +			cbm_cpu_update((void *)i);
>
> So this is called via
>
>   intel_rdt_cpu_notifier(CPU_ONLINE)
>     intel_rdt_cpu_start()
>       cbm_update_msrs()
> 	 cbm_cpu_update()
> 	   wrmsr()
>
> And runs on the CPU which initiated the hotplug and not on the newly
> online cpu. Pretty useless, right?

Will fix.

> > +	}
> > +}
> > +
> > +static inline void intel_rdt_cpu_start(int cpu)
> > +{
> > +	struct intel_pqr_state *state = &per_cpu(pqr_state, cpu);
> > +
> > +	state->closid = 0;
> > +	mutex_lock(&rdt_group_mutex);
> > +	if (rdt_cpumask_update(cpu))
> > +		cbm_update_msrs();
> > +	mutex_unlock(&rdt_group_mutex);
> > +}
> > +
> > +static void intel_rdt_cpu_exit(unsigned int cpu)
> > +{
> > +	int i;
> > +
> > +	mutex_lock(&rdt_group_mutex);
> > +	if (!cpumask_test_and_clear_cpu(cpu, &rdt_cpumask)) {
> > +		mutex_unlock(&rdt_group_mutex);
> > +		return;
> > +	}
> > +
> > +	i = cpumask_any_online_but(topology_core_cpumask(cpu), cpu);
> > +	if (i < nr_cpu_ids)
> > +		cpumask_set_cpu(i, &rdt_cpumask);
> > +	mutex_unlock(&rdt_group_mutex);
>
> Same issue as in the cqm patch.

will fix.
yes this may risk the package to not have some updates.

Thanks,
Vikas

> Thanks,
>
> 	tglx
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/