On 7/1/24 04:09, Ming Lei wrote:
On Thu, Jun 27, 2024 at 04:10:53PM +0200, Daniel Wagner wrote:
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.
Fixes: 11ea68f553e2 ("genirq, sched/isolation: Isolate from handling managed interrupts")
Signed-off-by: Daniel Wagner <dwagner@xxxxxxx>
---
lib/group_cpus.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 73 insertions(+), 2 deletions(-)
diff --git a/lib/group_cpus.c b/lib/group_cpus.c
index ee272c4cefcc..19fb7186f9d4 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
*
* Return: cpumask array if successful, NULL otherwise. And each element
@@ -344,7 +345,7 @@ 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)
+static struct cpumask *group_possible_cpus_evenly(unsigned int numgrps)
{
unsigned int curgrp = 0, nr_present = 0, nr_others = 0;
cpumask_var_t *node_to_cpumask;
@@ -423,6 +424,76 @@ struct cpumask *group_cpus_evenly(unsigned int numgrps)
}
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
+ *
+ * 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)
+{
+ 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;
+ }
+ return masks;
+}
+
+/**
+ * group_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality
+ * @numgrps: number of groups
+ *
+ * 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)
+{
+ const struct cpumask *hk_mask;
+
+ hk_mask = housekeeping_cpumask(HK_TYPE_MANAGED_IRQ);
+ if (!cpumask_empty(hk_mask))
+ return group_mask_cpus_evenly(numgrps, hk_mask);
+
+ return group_possible_cpus_evenly(numgrps);
Since this patch, some isolated CPUs may not be covered in
blk-mq queue mapping.
Meantime people still may submit IO workload from isolated CPUs
such as by 'taskset -c', blk-mq may not work well for this situation,
for example, IO hang may be caused during cpu hotplug.
I did see this kind of usage in some RH Openshift workloads.
If blk-mq problem can be solved, I am fine with this kind of
change.
That was kinda the idea of this patchset; when 'isolcpus' is active any
in-kernel driver can only run on the housekeeping CPUs, and I/O from the
isolcpus is impossible.
(Otherwise they won't be isolated anymore, and the whole concepts
becomes ever so shaky.).
Consequently we should not spread blk-mq onto the isolcpus (which is
what this patchset attempts). We do need to check how we could inhibit
I/O from the isolcpus, though; not sure if we do that now.
Something we need to check.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
