[RFC 3/3] virtio-blk: use NUMA-aware memory allocation in probe

[Stefan Hajnoczi <stefanha@redhat.com>]

Allocate frequently-accessed data structures from the NUMA node
associated with this device to avoid slow cross-NUMA node memory
accesses.

Only the following memory allocations are made NUMA-aware:

1. Called during probe. If called in the data path then hopefully we're
   executing on a CPU in the same NUMA node as the device. If the CPU is
   not in the right NUMA node then it's unclear whether forcing memory
   allocations to use the device's NUMA node will increase or decrease
   performance.

2. Memory will be frequently accessed from the data path. There is no
   need to worry about data that is not accessed from
   performance-critical code paths.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 drivers/block/virtio_blk.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 9d21bf0f155e..40845e9ad3b1 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -482,6 +482,7 @@ static int init_vq(struct virtio_blk *vblk)
 	unsigned short num_vqs;
 	struct virtio_device *vdev = vblk->vdev;
 	struct irq_affinity desc = { 0, };
+	int node = dev_to_node(&vdev->dev);
 
 	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_MQ,
 				   struct virtio_blk_config, num_queues,
@@ -491,7 +492,8 @@ static int init_vq(struct virtio_blk *vblk)
 
 	num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs);
 
-	vblk->vqs = kmalloc_array(num_vqs, sizeof(*vblk->vqs), GFP_KERNEL);
+	vblk->vqs = kmalloc_array_node(num_vqs, sizeof(*vblk->vqs),
+				       GFP_KERNEL, node);
 	if (!vblk->vqs)
 		return -ENOMEM;
 
@@ -683,6 +685,7 @@ module_param_named(queue_depth, virtblk_queue_depth, uint, 0444);
 
 static int virtblk_probe(struct virtio_device *vdev)
 {
+	int node = dev_to_node(&vdev->dev);
 	struct virtio_blk *vblk;
 	struct request_queue *q;
 	int err, index;
@@ -714,7 +717,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 
 	/* We need an extra sg elements at head and tail. */
 	sg_elems += 2;
-	vdev->priv = vblk = kmalloc(sizeof(*vblk), GFP_KERNEL);
+	vdev->priv = vblk = kmalloc_node(sizeof(*vblk), GFP_KERNEL, node);
 	if (!vblk) {
 		err = -ENOMEM;
 		goto out_free_index;
-- 
2.26.2