kyber: don't make domain token sbitmap larger than necessary

The domain token sbitmaps are currently initialized to the device queue
depth or 256, whichever is larger, and immediately resized to the
maximum depth for that domain (256, 128, or 64 for read, write, and
other, respectively). The sbitmap is never resized larger than that, so
it's unnecessary to allocate a bitmap larger than the maximum depth.
Let's just allocate it to the maximum depth to begin with. This will use
marginally less memory, and more importantly, give us a more appropriate
number of bits per sbitmap word.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index 95d062c07c61e7f64111c85f6d4095f47b79f71a..08eb5295c18da2ef42c2857a179aaf4e11ba96a5 100644 (file)
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -40,8 +40,6 @@ enum {
 };
 
 enum {
-       KYBER_MIN_DEPTH = 256,
-
        /*
         * In order to prevent starvation of synchronous requests by a flood of
         * asynchronous requests, we reserve 25% of requests for synchronous
@@ -305,7 +303,6 @@ static int kyber_bucket_fn(const struct request *rq)
 static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
 {
        struct kyber_queue_data *kqd;
-       unsigned int max_tokens;
        unsigned int shift;
        int ret = -ENOMEM;
        int i;
@@ -320,25 +317,17 @@ static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
        if (!kqd->cb)
                goto err_kqd;
 
-       /*
-        * The maximum number of tokens for any scheduling domain is at least
-        * the queue depth of a single hardware queue. If the hardware doesn't
-        * have many tags, still provide a reasonable number.
-        */
-       max_tokens = max_t(unsigned int, q->tag_set->queue_depth,
-                          KYBER_MIN_DEPTH);
        for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
                WARN_ON(!kyber_depth[i]);
                WARN_ON(!kyber_batch_size[i]);
                ret = sbitmap_queue_init_node(&kqd->domain_tokens[i],
-                                             max_tokens, -1, false, GFP_KERNEL,
-                                             q->node);
+                                             kyber_depth[i], -1, false,
+                                             GFP_KERNEL, q->node);
                if (ret) {
                        while (--i >= 0)
                                sbitmap_queue_free(&kqd->domain_tokens[i]);
                        goto err_cb;
                }
-               sbitmap_queue_resize(&kqd->domain_tokens[i], kyber_depth[i]);
        }
 
        shift = kyber_sched_tags_shift(kqd);