From fc1bc35443741e132dd0118e8dbac53f69a6f76e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matias=20Bj=C3=B8rling?= <m@bjorling.me>
Date: Sat, 21 Dec 2013 00:11:01 +0100
Subject: [PATCH] null_blk: support submit_queues on use_per_node_hctx
In the case of both the submit_queues param and use_per_node_hctx param
are used. We limit the number af submit_queues to the number of online
nodes.
If the submit_queues is a multiple of nr_online_nodes, its trivial. Simply map
them to the nodes. For example: 8 submit queues are mapped as node0[0,1],
node1[2,3], ...
If uneven, we are left with an uneven number of submit_queues that must be
mapped. These are mapped toward the first node and onward. E.g. 5
submit queues mapped onto 4 nodes are mapped as node0[0,1], node1[2], ...
Signed-off-by: Matias Bjorling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
drivers/block/null_blk.c | 39 +++++++++++++++++++++++++++++++++++----
1 file changed, 35 insertions(+), 4 deletions(-)
diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 9b0311b61fe1..528f4e47f38e 100644
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -1,4 +1,5 @@
#include <linux/module.h>
+
#include <linux/moduleparam.h>
#include <linux/sched.h>
#include <linux/fs.h>
@@ -346,8 +347,37 @@ static int null_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *rq)
static struct blk_mq_hw_ctx *null_alloc_hctx(struct blk_mq_reg *reg, unsigned int hctx_index)
{
- return kzalloc_node(sizeof(struct blk_mq_hw_ctx), GFP_KERNEL,
- hctx_index);
+ int b_size = DIV_ROUND_UP(reg->nr_hw_queues, nr_online_nodes);
+ int tip = (reg->nr_hw_queues % nr_online_nodes);
+ int node = 0, i, n;
+
+ /*
+ * Split submit queues evenly wrt to the number of nodes. If uneven,
+ * fill the first buckets with one extra, until the rest is filled with
+ * no extra.
+ */
+ for (i = 0, n = 1; i < hctx_index; i++, n++) {
+ if (n % b_size == 0) {
+ n = 0;
+ node++;
+
+ tip--;
+ if (!tip)
+ b_size = reg->nr_hw_queues / nr_online_nodes;
+ }
+ }
+
+ /*
+ * A node might not be online, therefore map the relative node id to the
+ * real node id.
+ */
+ for_each_online_node(n) {
+ if (!node)
+ break;
+ node--;
+ }
+
+ return kzalloc_node(sizeof(struct blk_mq_hw_ctx), GFP_KERNEL, n);
}
static void null_free_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_index)
@@ -591,10 +621,11 @@ static int __init null_init(void)
#endif
if (queue_mode == NULL_Q_MQ && use_per_node_hctx) {
- if (submit_queues > 0)
+ if (submit_queues < nr_online_nodes) {
pr_warn("null_blk: submit_queues param is set to %u.",
nr_online_nodes);
- submit_queues = nr_online_nodes;
+ submit_queues = nr_online_nodes;
+ }
} else if (submit_queues > nr_cpu_ids)
submit_queues = nr_cpu_ids;
else if (!submit_queues)
--
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