On Thursday 23 March 2017 06:39 PM, Gautham R Shenoy wrote:

Hi Maddy, Hemant, Anju,

On Thu, Mar 16, 2017 at 01:05:02PM +0530, Madhavan Srinivasan wrote:

[..snip..]

quoted

+
+static void core_imc_change_cpu_context(int old_cpu, int new_cpu)
+{
+	if (!core_imc_pmu)
+		return;
+	perf_pmu_migrate_context(&core_imc_pmu->pmu, old_cpu, new_cpu);
+}
+
+
+static int ppc_core_imc_cpu_online(unsigned int cpu)
+{
+	int ret;
+
+	/* If a cpu for this core is already set, then, don't do anything */
+	ret = cpumask_any_and(&core_imc_cpumask,
+				 cpu_sibling_mask(cpu));
+	if (ret < nr_cpu_ids)
+		return 0;
+
+	/* Else, set the cpu in the mask, and change the context */
+	cpumask_set_cpu(cpu, &core_imc_cpumask);
+	core_imc_change_cpu_context(-1, cpu);

So, in the core case, we are ok as long as any cpu in the core is
present in the imc_cpumask. It need not have to be the smallest online
cpu in the core.

Can the same logic be applied to the earlier nest case ?

Yes. This makes sense. Let me look at this.

Thanks for review
Maddy

We can have a single function for cpu_offline and cpu_online which
implements these checks and sets the cpu bit if required.

ppc_entity_imc_cpu_offline(unsigned int cpu, cpumask_t
			   entity_imc_mask,
			   entity_imc_change_cpu_context_fn)
{
	.
	.
	.
	
}


static ppc_nest_imc_cpu_offline(unsigned int cpu)
{
	return ppc_entity_imc_cpu_offline(cpu, nest_imc_mask,
					  nest_imc_change_cpu_context);
}

And similar ones for core imc and thread imc.

Does this sound reasonable ?

quoted

+	return 0;
+}
+
+static int ppc_core_imc_cpu_offline(unsigned int cpu)
+{
+	int target;
+	unsigned int ncpu;
+
+	/*
+	 * clear this cpu out of the mask, if not present in the mask,
+	 * don't bother doing anything.
+	 */
+	if (!cpumask_test_and_clear_cpu(cpu, &core_imc_cpumask))
+		return 0;
+
+	/* Find any online cpu in that core except the current "cpu" */
+	ncpu = cpumask_any_but(cpu_sibling_mask(cpu), cpu);
+
+	if (ncpu < nr_cpu_ids) {
+		target = ncpu;
+		cpumask_set_cpu(target, &core_imc_cpumask);
+	} else
+		target = -1;
+
+	/* migrate the context */
+	core_imc_change_cpu_context(cpu, target);
+
+	return 0;
+}
+

--
Thanks and Regards
gautham.