IMO we must fulfil the user wish to connect to N queues and not reduce
it because of affinity overlaps. So in order to push Leon's patch we
must also fix the blk_mq_rdma_map_queues to do a best effort mapping
according the affinity and map the rest in naive way (in that way we
will *always* map all the queues).
That is what I would expect also. For example, in my node, where there are
16 cpus, and 2 numa nodes, I observe much better nvmf IOPS performance by
setting up my 16 driver completion event queues such that each is bound to a
node-local cpu. So I end up with each nodel-local cpu having 2 queues bound
to it. W/O adding support in iw_cxgb4 for ib_get_vector_affinity(), this
works fine. I assumed adding ib_get_vector_affinity() would allow this to
all "just work" by default, but I'm running into this connection failure
issue.
I don't understand exactly what the blk_mq layer is trying to do, but I
assume it has ingress event queues and processing that it trying to align
with the drivers ingress cq event handling, so everybody stays on the same
cpu (or at least node). But something else is going on. Is there
documentation on how this works somewhere?
Does this (untested) patch help?
--
diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
index 3eb169f15842..dbe962cb537d 100644
--- a/block/blk-mq-cpumap.c
+++ b/block/blk-mq-cpumap.c
@@ -30,29 +30,34 @@ static int get_first_sibling(unsigned int cpu)
return cpu;
}
-int blk_mq_map_queues(struct blk_mq_tag_set *set)
+void blk_mq_map_queue(struct blk_mq_tag_set *set, unsigned int cpu)
{
unsigned int *map = set->mq_map;
unsigned int nr_queues = set->nr_hw_queues;
- unsigned int cpu, first_sibling;
+ unsigned int first_sibling;
- for_each_possible_cpu(cpu) {
- /*
- * First do sequential mapping between CPUs and queues.
- * In case we still have CPUs to map, and we have some
number of
- * threads per cores then map sibling threads to the
same queue for
- * performace optimizations.
- */
- if (cpu < nr_queues) {
+ /*
+ * First do sequential mapping between CPUs and queues.
+ * In case we still have CPUs to map, and we have some number of
+ * threads per cores then map sibling threads to the same queue for
+ * performace optimizations.
+ */
+ if (cpu < nr_queues) {
+ map[cpu] = cpu_to_queue_index(nr_queues, cpu);
+ } else {
+ first_sibling = get_first_sibling(cpu);
+ if (first_sibling == cpu)
map[cpu] = cpu_to_queue_index(nr_queues, cpu);
- } else {
- first_sibling = get_first_sibling(cpu);
- if (first_sibling == cpu)
- map[cpu] = cpu_to_queue_index(nr_queues,
cpu);
- else
- map[cpu] = map[first_sibling];
- }
+ else
+ map[cpu] = map[first_sibling];
}
+}
+EXPORT_SYMBOL_GPL(blk_mq_map_queue);
+
+int blk_mq_map_queues(struct blk_mq_tag_set *set)
+{
+ for_each_possible_cpu(cpu)
+ blk_mq_map_queue(set, cpu);
return 0;
}
diff --git a/block/blk-mq-rdma.c b/block/blk-mq-rdma.c
index 996167f1de18..5e91789bea5b 100644
--- a/block/blk-mq-rdma.c
+++ b/block/blk-mq-rdma.c
@@ -35,6 +35,10 @@ int blk_mq_rdma_map_queues(struct blk_mq_tag_set *set,
const struct cpumask *mask;
unsigned int queue, cpu;
+ /* reset all to */
+ for_each_possible_cpu(cpu)
+ set->mq_map[cpu] = UINT_MAX;
+
for (queue = 0; queue < set->nr_hw_queues; queue++) {
mask = ib_get_vector_affinity(dev, first_vec + queue);
if (!mask)
@@ -44,6 +48,11 @@ int blk_mq_rdma_map_queues(struct blk_mq_tag_set *set,
set->mq_map[cpu] = queue;
}
+ for_each_possible_cpu(cpu) {
+ if (set->mq_map[cpu] == UINT_MAX)
+ blk_mq_map_queue(set, cpu);
+ }
+
return 0;
fallback:
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index e3147eb74222..7a9848a82475 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -283,6 +283,7 @@ int blk_mq_freeze_queue_wait_timeout(struct
request_queue *q,
unsigned long timeout);
int blk_mq_map_queues(struct blk_mq_tag_set *set);
+void blk_mq_map_queue(struct blk_mq_tag_set *set, unsigned int cpu);
void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int
nr_hw_queues);
void blk_mq_quiesce_queue_nowait(struct request_queue *q);
--
It really is still a best effort thing...
