diff mbox series

[RFC,3/5] kyber: don't make domain token sbitmap larger than necessary

Message ID 47e82117e82563637b9a7091b827267f6874b9d2.1533846185.git.osandov@fb.com (mailing list archive)
State New, archived
Headers show
Series kyber: better heuristics | expand

Commit Message

Omar Sandoval Aug. 9, 2018, 8:26 p.m. UTC 
From: Omar Sandoval <osandov@fb.com>

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>
---
 block/kyber-iosched.c | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)
diff mbox series

Patch

diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index 95d062c07c61..08eb5295c18d 100644
--- 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);