[PATCH v6 7/9] lib/group_cpus: honor housekeeping config when grouping CPUs

Daniel Wagner
2025-04-24T18:20:06Z

group_cpus_evenly distributes all present CPUs into groups. This ignores
the isolcpus configuration and assigns isolated CPUs into the groups.

Make group_cpus_evenly aware of isolcpus configuration and use the
housekeeping CPU mask as base for distributing the available CPUs into
groups.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Daniel Wagner <wagi@kernel.org>
---
lib/group_cpus.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 79 insertions(+), 3 deletions(-)

diff --git a/lib/group_cpus.c b/lib/group_cpus.c
index 016c6578a07616959470b47121459a16a1bc99e5..707997bca55344b18f63ccfa539ba77a89d8acb6 100644
--- a/lib/group_cpus.c
+++ b/lib/group_cpus.c
@@ -8,6 +8,7 @@
#include <linux/cpu.h>
#include <linux/sort.h>
#include <linux/group_cpus.h>
+#include <linux/sched/isolation.h>

#ifdef CONFIG_SMP

@@ -330,7 +331,7 @@ static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps,
}

/**
- * group_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality
+ * group_possible_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality
* @numgrps: number of groups
* @nummasks: number of initialized cpumasks
*
@@ -346,8 +347,8 @@ static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps,
* We guarantee in the resulted grouping that all CPUs are covered, and
* no same CPU is assigned to multiple groups
*/
-struct cpumask *group_cpus_evenly(unsigned int numgrps,
- unsigned int *nummasks)
+static struct cpumask *group_possible_cpus_evenly(unsigned int numgrps,
+ unsigned int *nummasks)
{
unsigned int curgrp = 0, nr_present = 0, nr_others = 0;
cpumask_var_t *node_to_cpumask;
@@ -427,6 +428,81 @@ struct cpumask *group_cpus_evenly(unsigned int numgrps,
*nummasks = nr_present + nr_others;
return masks;
}
+
+/**
+ * group_mask_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality
+ * @numgrps: number of groups
+ * @cpu_mask: CPU to consider for the grouping
+ * @nummasks: number of initialized cpusmasks
+ *
+ * Return: cpumask array if successful, NULL otherwise. And each element
+ * includes CPUs assigned to this group.
+ *
+ * Try to put close CPUs from viewpoint of CPU and NUMA locality into
+ * same group. Allocate present CPUs on these groups evenly.
+ */
+static struct cpumask *group_mask_cpus_evenly(unsigned int numgrps,
+ const struct cpumask *cpu_mask,
+ unsigned int *nummasks)
+{
+ cpumask_var_t *node_to_cpumask;
+ cpumask_var_t nmsk;
+ int ret = -ENOMEM;
+ struct cpumask *masks = NULL;
+
+ if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
+ return NULL;
+
+ node_to_cpumask = alloc_node_to_cpumask();
+ if (!node_to_cpumask)
+ goto fail_nmsk;
+
+ masks = kcalloc(numgrps, sizeof(*masks), GFP_KERNEL);
+ if (!masks)
+ goto fail_node_to_cpumask;
+
+ build_node_to_cpumask(node_to_cpumask);
+
+ ret = __group_cpus_evenly(0, numgrps, node_to_cpumask, cpu_mask, nmsk,
+ masks);
+
+fail_node_to_cpumask:
+ free_node_to_cpumask(node_to_cpumask);
+
+fail_nmsk:
+ free_cpumask_var(nmsk);
+ if (ret < 0) {
+ kfree(masks);
+ return NULL;
+ }
+ *nummasks = ret;
+ return masks;
+}
+
+/**
+ * group_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality
+ * @numgrps: number of groups
+ * @nummasks: number of initialized cpusmasks
+ *
+ * Return: cpumask array if successful, NULL otherwise.
+ *
+ * group_possible_cpus_evently() is used for distributing the cpus on all
+ * possible cpus in absence of isolcpus command line argument.
+ * group_mask_cpu_evenly() is used when the isolcpus command line
+ * argument is used with managed_irq option. In this case only the
+ * housekeeping CPUs are considered.
+ */
+struct cpumask *group_cpus_evenly(unsigned int numgrps,
+ unsigned int *nummasks)
+{
+ if (housekeeping_enabled(HK_TYPE_IO_QUEUE)) {
+ return group_mask_cpus_evenly(numgrps,
+ housekeeping_cpumask(HK_TYPE_IO_QUEUE),
+ nummasks);
+ }
+
+ return group_possible_cpus_evenly(numgrps, nummasks);
+}
#else /* CONFIG_SMP */
struct cpumask *group_cpus_evenly(unsigned int numgrps,
unsigned int *nummasks)

--
2.49.0