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Commit df52f671 authored by Oliver O'Halloran's avatar Oliver O'Halloran Committed by Michael Ellerman
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powerpc/smp: Rework CPU topology construction 



The CPU scheduler topology is constructed from a number of per-cpu
cpumasks which describe which sets of logical CPUs are related in some
fashion. Current code that handles constructing these masks when CPUs
are hot(un)plugged can be simplified a bit by exploiting the fact that
the scheduler requires higher levels of the toplogy (e.g package level
groupings) to be supersets of the lower levels (e.g.  threas in a core).
This patch reworks the cpumask construction to be simpler and easier to
extend with extra topology levels.

Signed-off-by: default avatarOliver O'Halloran <oohall@gmail.com>
[mpe: Fix CONFIG_HOTPLUG_CPU=n build]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent e3d8b67e

arch/powerpc/kernel/smp.c

+86 −66
Original line number Diff line number Diff line
@@ -571,6 +571,26 @@ static void smp_store_cpu_info(int id) 
#endif

}



/*

 * Relationships between CPUs are maintained in a set of per-cpu cpumasks so

 * rather than just passing around the cpumask we pass around a function that

 * returns the that cpumask for the given CPU.

 */

static void set_cpus_related(int i, int j, struct cpumask *(*get_cpumask)(int))

{

	cpumask_set_cpu(i, get_cpumask(j));

	cpumask_set_cpu(j, get_cpumask(i));

}



#ifdef CONFIG_HOTPLUG_CPU

static void set_cpus_unrelated(int i, int j,

		struct cpumask *(*get_cpumask)(int))

{

	cpumask_clear_cpu(i, get_cpumask(j));

	cpumask_clear_cpu(j, get_cpumask(i));

}

#endif



void __init smp_prepare_cpus(unsigned int max_cpus)

{

	unsigned int cpu;
@@ -602,6 +622,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus) 
		}

	}



	/* Init the cpumasks so the boot CPU is related to itself */

	cpumask_set_cpu(boot_cpuid, cpu_sibling_mask(boot_cpuid));

	cpumask_set_cpu(boot_cpuid, cpu_core_mask(boot_cpuid));
@@ -828,24 +849,6 @@ int cpu_first_thread_of_core(int core) 
}

EXPORT_SYMBOL_GPL(cpu_first_thread_of_core);



static void traverse_siblings_chip_id(int cpu, bool add, int chipid)

{

	const struct cpumask *mask = add ? cpu_online_mask : cpu_present_mask;

	int i;



	for_each_cpu(i, mask) {

		if (cpu_to_chip_id(i) == chipid) {

			if (add) {

				cpumask_set_cpu(cpu, cpu_core_mask(i));

				cpumask_set_cpu(i, cpu_core_mask(cpu));

			} else {

				cpumask_clear_cpu(cpu, cpu_core_mask(i));

				cpumask_clear_cpu(i, cpu_core_mask(cpu));

			}

		}

	}

}



/* Must be called when no change can occur to cpu_present_mask,

 * i.e. during cpu online or offline.

 */
@@ -868,46 +871,85 @@ static struct device_node *cpu_to_l2cache(int cpu) 
	return cache;

}



static void traverse_core_siblings(int cpu, bool add)

static bool update_mask_by_l2(int cpu, struct cpumask *(*mask_fn)(int))

{

	struct device_node *l2_cache, *np;

	const struct cpumask *mask;

	int chip_id;

	int i;



	/* threads that share a chip-id are considered siblings */

	chip_id = cpu_to_chip_id(cpu);



	if (chip_id >= 0) {

		traverse_siblings_chip_id(cpu, add, chip_id);

		return;

	}



	l2_cache = cpu_to_l2cache(cpu);

	mask = add ? cpu_online_mask : cpu_present_mask;

	for_each_cpu(i, mask) {

	if (!l2_cache)

		return false;



	for_each_cpu(i, cpu_online_mask) {

		/*

		 * when updating the marks the current CPU has not been marked

		 * online, but we need to update the cache masks

		 */

		np = cpu_to_l2cache(i);

		if (!np)

			continue;

		if (np == l2_cache) {

			if (add) {

				cpumask_set_cpu(cpu, cpu_core_mask(i));

				cpumask_set_cpu(i, cpu_core_mask(cpu));

			} else {

				cpumask_clear_cpu(cpu, cpu_core_mask(i));

				cpumask_clear_cpu(i, cpu_core_mask(cpu));

			}

		}



		if (np == l2_cache)

			set_cpus_related(cpu, i, mask_fn);



		of_node_put(np);

	}

	of_node_put(l2_cache);



	return true;

}



#ifdef CONFIG_HOTPLUG_CPU

static void remove_cpu_from_masks(int cpu)

{

	int i;



	/* NB: cpu_core_mask is a superset of the others */

	for_each_cpu(i, cpu_core_mask(cpu)) {

		set_cpus_unrelated(cpu, i, cpu_core_mask);

		set_cpus_unrelated(cpu, i, cpu_sibling_mask);

	}

}

#endif



static void add_cpu_to_masks(int cpu)

{

	int first_thread = cpu_first_thread_sibling(cpu);

	int chipid = cpu_to_chip_id(cpu);

	int i;



	/*

	 * This CPU will not be in the online mask yet so we need to manually

	 * add it to it's own thread sibling mask.

	 */

	cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));



	for (i = first_thread; i < first_thread + threads_per_core; i++)

		if (cpu_online(i))

			set_cpus_related(i, cpu, cpu_sibling_mask);



	/*

	 * Copy the thread sibling into core sibling mask, and

	 * add CPUs that share a chip or an L2 to the core sibling

	 * mask.

	 */

	for_each_cpu(i, cpu_sibling_mask(cpu))

		set_cpus_related(cpu, i, cpu_core_mask);



	if (chipid == -1) {

		update_mask_by_l2(cpu, cpu_core_mask);

		return;

	}



	for_each_cpu(i, cpu_online_mask)

		if (cpu_to_chip_id(i) == chipid)

			set_cpus_related(cpu, i, cpu_core_mask);

}



/* Activate a secondary processor. */

void start_secondary(void *unused)

{

	unsigned int cpu = smp_processor_id();

	int i, base;



	mmgrab(&init_mm);

	current->active_mm = &init_mm;
@@ -930,22 +972,8 @@ void start_secondary(void *unused) 


	vdso_getcpu_init();

#endif

	/* Update sibling maps */

	base = cpu_first_thread_sibling(cpu);

	for (i = 0; i < threads_per_core; i++) {

		if (cpu_is_offline(base + i) && (cpu != base + i))

			continue;

		cpumask_set_cpu(cpu, cpu_sibling_mask(base + i));

		cpumask_set_cpu(base + i, cpu_sibling_mask(cpu));



		/* cpu_core_map should be a superset of

		 * cpu_sibling_map even if we don't have cache

		 * information, so update the former here, too.

		 */

		cpumask_set_cpu(cpu, cpu_core_mask(base + i));

		cpumask_set_cpu(base + i, cpu_core_mask(cpu));

	}

	traverse_core_siblings(cpu, true);

	/* Update topology CPU masks */

	add_cpu_to_masks(cpu);



	set_numa_node(numa_cpu_lookup_table[cpu]);

	set_numa_mem(local_memory_node(numa_cpu_lookup_table[cpu]));
@@ -1008,7 +1036,6 @@ void __init smp_cpus_done(unsigned int max_cpus) 
int __cpu_disable(void)

{

	int cpu = smp_processor_id();

	int base, i;

	int err;



	if (!smp_ops->cpu_disable)
@@ -1019,14 +1046,7 @@ int __cpu_disable(void) 
		return err;



	/* Update sibling maps */

	base = cpu_first_thread_sibling(cpu);

	for (i = 0; i < threads_per_core && base + i < nr_cpu_ids; i++) {

		cpumask_clear_cpu(cpu, cpu_sibling_mask(base + i));

		cpumask_clear_cpu(base + i, cpu_sibling_mask(cpu));

		cpumask_clear_cpu(cpu, cpu_core_mask(base + i));

		cpumask_clear_cpu(base + i, cpu_core_mask(cpu));

	}

	traverse_core_siblings(cpu, false);

	remove_cpu_from_masks(cpu);



	return 0;

}