diff mbox series

[v6,2/9] blk-mq: add number of queue calc helper

Message ID 20250424-isolcpus-io-queues-v6-2-9a53a870ca1f@kernel.org
State New
Headers show
Series blk: honor isolcpus configuration | expand

Commit Message

Daniel Wagner April 24, 2025, 6:19 p.m. UTC 
Multiqueue devices should only allocate queues for the housekeeping CPUs
when isolcpus=io_queue is set. This avoids that the isolated CPUs get
disturbed with OS workload.

Add two variants of helpers which calculates the correct number of
queues which should be used. The need for two variants is necessary
because some drivers calculate their max number of queues based on the
possible CPU mask, others based on the online CPU mask.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Daniel Wagner <wagi@kernel.org>
---
 block/blk-mq-cpumap.c  | 45 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/blk-mq.h |  2 ++
 2 files changed, 47 insertions(+)
diff mbox series

Patch

diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
index 269161252add756897fce1b65cae5b2e6aebd647..6e6b3e989a5676186b5a31296a1b94b7602f1542 100644
--- a/block/blk-mq-cpumap.c
+++ b/block/blk-mq-cpumap.c
@@ -12,10 +12,55 @@ 
 #include <linux/cpu.h>
 #include <linux/group_cpus.h>
 #include <linux/device/bus.h>
+#include <linux/sched/isolation.h>
 
 #include "blk.h"
 #include "blk-mq.h"
 
+static unsigned int blk_mq_num_queues(const struct cpumask *mask,
+				      unsigned int max_queues)
+{
+	unsigned int num;
+
+	if (housekeeping_enabled(HK_TYPE_MANAGED_IRQ))
+		mask = housekeeping_cpumask(HK_TYPE_MANAGED_IRQ);
+
+	num = cpumask_weight(mask);
+	return min_not_zero(num, max_queues);
+}
+
+/**
+ * blk_mq_num_possible_queues - Calc nr of queues for multiqueue devices
+ * @max_queues:	The maximal number of queues the hardware/driver
+ *		supports. If max_queues is 0, the argument is
+ *		ignored.
+ *
+ * Calculate the number of queues which should be used for a multiqueue
+ * device based on the number of possible cpu. The helper is considering
+ * isolcpus settings.
+ */
+unsigned int blk_mq_num_possible_queues(unsigned int max_queues)
+{
+	return blk_mq_num_queues(cpu_possible_mask, max_queues);
+}
+EXPORT_SYMBOL_GPL(blk_mq_num_possible_queues);
+
+/**
+ * blk_mq_num_online_queues - Calc nr of queues for multiqueue devices
+ * @max_queues:	The maximal number of queues the hardware/driver
+ *		supports. If max_queues is 0, the argument is
+ *		ignored.
+ *
+ * Calculate the number of queues which should be used for a multiqueue
+ * device based on the number of online cpus. The helper is considering
+ * isolcpus settings.
+ */
+unsigned int blk_mq_num_online_queues(unsigned int max_queues)
+{
+	return blk_mq_num_queues(cpu_online_mask, max_queues);
+}
+EXPORT_SYMBOL_GPL(blk_mq_num_online_queues);
+
 void blk_mq_map_queues(struct blk_mq_queue_map *qmap)
 {
 	const struct cpumask *masks;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 8eb9b3310167c36f8a67ee8756a97d1274f8e73b..feed1dcaeef51c8db49d3fe667c64ecc824ce655 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -941,6 +941,8 @@  int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
 void blk_mq_unfreeze_queue_non_owner(struct request_queue *q);
 void blk_freeze_queue_start_non_owner(struct request_queue *q);
 
+unsigned int blk_mq_num_possible_queues(unsigned int max_queues);
+unsigned int blk_mq_num_online_queues(unsigned int max_queues);
 void blk_mq_map_queues(struct blk_mq_queue_map *qmap);
 void blk_mq_map_hw_queues(struct blk_mq_queue_map *qmap,
 			  struct device *dev, unsigned int offset);