[PATCH 2/4] powerpc/smp: Rework CPU topology construction
Oliver O'Halloran
oohall at gmail.com
Thu Jun 29 17:12:54 AEST 2017
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: Oliver O'Halloran <oohall at gmail.com>
---
arch/powerpc/kernel/smp.c | 148 +++++++++++++++++++++++++---------------------
1 file changed, 82 insertions(+), 66 deletions(-)
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 40f1f268be83..4c50f5fe5366 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -569,6 +569,24 @@ 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));
+}
+
+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));
+}
+
void __init smp_prepare_cpus(unsigned int max_cpus)
{
unsigned int cpu;
@@ -600,6 +618,7 @@ 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));
@@ -827,24 +846,6 @@ 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.
*/
@@ -867,46 +868,83 @@ 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;
+}
+
+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);
+ }
+}
+
+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;
@@ -929,22 +967,8 @@ 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]));
@@ -1015,7 +1039,6 @@ 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)
@@ -1026,14 +1049,7 @@ 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;
}
--
2.9.4
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