ublk: implement NUMA-aware memory allocation

Implement NUMA-friendly memory allocation for ublk driver to improve
performance on multi-socket systems.

This commit includes the following changes:

1. Rename __queues to queues, dropping the __ prefix since the field is
   now accessed directly throughout the codebase rather than only through
   the ublk_get_queue() helper.

2. Remove the queue_size field from struct ublk_device as it is no longer
   needed.

3. Move queue allocation and deallocation into ublk_init_queue() and
   ublk_deinit_queue() respectively, improving encapsulation. This
   simplifies ublk_init_queues() and ublk_deinit_queues() to just
   iterate and call the per-queue functions.

4. Add ublk_get_queue_numa_node() helper function to determine the
   appropriate NUMA node for a queue by finding the first CPU mapped
   to that queue via tag_set.map[HCTX_TYPE_DEFAULT].mq_map[] and
   converting it to a NUMA node using cpu_to_node(). This function is
   called internally by ublk_init_queue() to determine the allocation
   node.

5. Allocate each queue structure on its local NUMA node using
   kvzalloc_node() in ublk_init_queue().

6. Allocate the I/O command buffer on the same NUMA node using
   alloc_pages_node().

This reduces memory access latency on multi-socket NUMA systems by
ensuring each queue's data structures are local to the CPUs that
access them.

Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 2569566bf5e6e157b1e437d8bfeac257d5cd050c..d920f7cf4dad2a52fa6672e55d72971c00de0c2e 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -209,9 +209,6 @@ struct ublk_queue {
 struct ublk_device {
        struct gendisk          *ub_disk;
 
-       char    *__queues;
-
-       unsigned int    queue_size;
        struct ublksrv_ctrl_dev_info    dev_info;
 
        struct blk_mq_tag_set   tag_set;
@@ -239,6 +236,8 @@ struct ublk_device {
        bool canceling;
        pid_t   ublksrv_tgid;
        struct delayed_work     exit_work;
+
+       struct ublk_queue       *queues[];
 };
 
 /* header of ublk_params */
@@ -781,7 +780,7 @@ static noinline void ublk_put_device(struct ublk_device *ub)
 static inline struct ublk_queue *ublk_get_queue(struct ublk_device *dev,
                int qid)
 {
-       return (struct ublk_queue *)&(dev->__queues[qid * dev->queue_size]);
+       return dev->queues[qid];
 }
 
 static inline bool ublk_rq_has_data(const struct request *rq)
@@ -2662,9 +2661,13 @@ static const struct file_operations ublk_ch_fops = {
 
 static void ublk_deinit_queue(struct ublk_device *ub, int q_id)
 {
-       int size = ublk_queue_cmd_buf_size(ub);
-       struct ublk_queue *ubq = ublk_get_queue(ub, q_id);
-       int i;
+       struct ublk_queue *ubq = ub->queues[q_id];
+       int size, i;
+
+       if (!ubq)
+               return;
+
+       size = ublk_queue_cmd_buf_size(ub);
 
        for (i = 0; i < ubq->q_depth; i++) {
                struct ublk_io *io = &ubq->ios[i];
@@ -2676,57 +2679,76 @@ static void ublk_deinit_queue(struct ublk_device *ub, int q_id)
 
        if (ubq->io_cmd_buf)
                free_pages((unsigned long)ubq->io_cmd_buf, get_order(size));
+
+       kvfree(ubq);
+       ub->queues[q_id] = NULL;
+}
+
+static int ublk_get_queue_numa_node(struct ublk_device *ub, int q_id)
+{
+       unsigned int cpu;
+
+       /* Find first CPU mapped to this queue */
+       for_each_possible_cpu(cpu) {
+               if (ub->tag_set.map[HCTX_TYPE_DEFAULT].mq_map[cpu] == q_id)
+                       return cpu_to_node(cpu);
+       }
+
+       return NUMA_NO_NODE;
 }
 
 static int ublk_init_queue(struct ublk_device *ub, int q_id)
 {
-       struct ublk_queue *ubq = ublk_get_queue(ub, q_id);
+       int depth = ub->dev_info.queue_depth;
+       int ubq_size = sizeof(struct ublk_queue) + depth * sizeof(struct ublk_io);
        gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO;
-       void *ptr;
+       struct ublk_queue *ubq;
+       struct page *page;
+       int numa_node;
        int size;
 
+       /* Determine NUMA node based on queue's CPU affinity */
+       numa_node = ublk_get_queue_numa_node(ub, q_id);
+
+       /* Allocate queue structure on local NUMA node */
+       ubq = kvzalloc_node(ubq_size, GFP_KERNEL, numa_node);
+       if (!ubq)
+               return -ENOMEM;
+
        spin_lock_init(&ubq->cancel_lock);
        ubq->flags = ub->dev_info.flags;
        ubq->q_id = q_id;
-       ubq->q_depth = ub->dev_info.queue_depth;
+       ubq->q_depth = depth;
        size = ublk_queue_cmd_buf_size(ub);
 
-       ptr = (void *) __get_free_pages(gfp_flags, get_order(size));
-       if (!ptr)
+       /* Allocate I/O command buffer on local NUMA node */
+       page = alloc_pages_node(numa_node, gfp_flags, get_order(size));
+       if (!page) {
+               kvfree(ubq);
                return -ENOMEM;
+       }
+       ubq->io_cmd_buf = page_address(page);
 
-       ubq->io_cmd_buf = ptr;
+       ub->queues[q_id] = ubq;
        ubq->dev = ub;
        return 0;
 }
 
 static void ublk_deinit_queues(struct ublk_device *ub)
 {
-       int nr_queues = ub->dev_info.nr_hw_queues;
        int i;
 
-       if (!ub->__queues)
-               return;
-
-       for (i = 0; i < nr_queues; i++)
+       for (i = 0; i < ub->dev_info.nr_hw_queues; i++)
                ublk_deinit_queue(ub, i);
-       kvfree(ub->__queues);
 }
 
 static int ublk_init_queues(struct ublk_device *ub)
 {
-       int nr_queues = ub->dev_info.nr_hw_queues;
-       int depth = ub->dev_info.queue_depth;
-       int ubq_size = sizeof(struct ublk_queue) + depth * sizeof(struct ublk_io);
-       int i, ret = -ENOMEM;
+       int i, ret;
 
-       ub->queue_size = ubq_size;
-       ub->__queues = kvcalloc(nr_queues, ubq_size, GFP_KERNEL);
-       if (!ub->__queues)
-               return ret;
-
-       for (i = 0; i < nr_queues; i++) {
-               if (ublk_init_queue(ub, i))
+       for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {
+               ret = ublk_init_queue(ub, i);
+               if (ret)
                        goto fail;
        }
 
@@ -3128,7 +3150,7 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header)
                goto out_unlock;
 
        ret = -ENOMEM;
-       ub = kzalloc(sizeof(*ub), GFP_KERNEL);
+       ub = kzalloc(struct_size(ub, queues, info.nr_hw_queues), GFP_KERNEL);
        if (!ub)
                goto out_unlock;
        mutex_init(&ub->mutex);