From: Ming Lin <ming.l@xxxxxxxxxxxxxxx>
Suppose that a system has 8 logical CPUs(4 cores with hyperthread)
and that 5 hardware queues are provided by a block driver.
With the current algorithm this will lead to the following assignment
of logical CPU to hardware queue:
HWQ 0: 0 1
HWQ 1: 2 3
HWQ 2: 4 5
HWQ 3: 6 7
HWQ 4: (none)
One way to fix it is to change the algorithm so the assignment may be:
HWQ 0: 0 1
HWQ 1: 2 3
HWQ 2: 4 5
HWQ 3: 6
HWQ 4: 7
This patch only checks if all HW queues are mapped to cpu.
blk_mq_init_queue() will fail if not all HW queues are mapped.
And it also fails when hardware queue numbers > cpu numbers.
Signed-off-by: Ming Lin <ming.l@xxxxxxxxxxxxxxxx>
---
block/blk-mq-cpumap.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
index 8764c24..5a88ac4 100644
--- a/block/blk-mq-cpumap.c
+++ b/block/blk-mq-cpumap.c
@@ -36,10 +36,17 @@ int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues,
{
unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
cpumask_var_t cpus;
+ int *queue_map;
- if (!alloc_cpumask_var(&cpus, GFP_ATOMIC))
+ queue_map = kzalloc(sizeof(int) * nr_queues, GFP_KERNEL);
+ if (!queue_map)
return 1;
+ if (!alloc_cpumask_var(&cpus, GFP_ATOMIC)) {
+ kfree(queue_map);
+ return 1;
+ }
+
cpumask_clear(cpus);
nr_cpus = nr_uniq_cpus = 0;
for_each_cpu(i, online_mask) {
@@ -54,7 +61,7 @@ int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues,
for_each_possible_cpu(i) {
if (!cpumask_test_cpu(i, online_mask)) {
map[i] = 0;
- continue;
+ goto mapped;
}
/*
@@ -65,7 +72,7 @@ int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues,
if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) {
map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue);
queue++;
- continue;
+ goto mapped;
}
/*
@@ -80,10 +87,22 @@ int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues,
queue++;
} else
map[i] = map[first_sibling];
+
+mapped:
+ /* i is cpu, map[i] is queue index */
+ queue_map[map[i]] = 1;
}
free_cpumask_var(cpus);
- return 0;
+
+ /* check if all queues are mapped to cpu */
+ for (i = 0; i < nr_queues; i++)
+ if (!queue_map[i])
+ break;
+
+ kfree(queue_map);
+
+ return i != nr_queues;
}
unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set)
--
1.9.1
--
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