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authorMing Lei <ming.lei@redhat.com>2021-01-22 05:33:12 +0300
committerMartin K. Petersen <martin.petersen@oracle.com>2021-03-05 01:36:59 +0300
commit2a5a24aa83382a88c43d18a901fab66e6ffe1199 (patch)
tree85d9a1aa8d76bb25fe9fdc56f9a1b74f575ce485 /block/blk-mq.c
parentd022d18c045fc2ccf92d0f14cf80f98eb0a8e119 (diff)
downloadlinux-2a5a24aa83382a88c43d18a901fab66e6ffe1199.tar.xz
scsi: blk-mq: Return budget token from .get_budget callback
SCSI uses a global atomic variable to track queue depth for each LUN/request queue. This doesn't scale well when there are lots of CPU cores and the disk is very fast. It has been observed that IOPS is affected a lot by tracking queue depth via sdev->device_busy in the I/O path. Return budget token from .get_budget callback. The budget token can be passed to driver so that we can replace the atomic variable with sbitmap_queue and alleviate the scaling problems that way. Link: https://lore.kernel.org/r/20210122023317.687987-9-ming.lei@redhat.com Cc: Omar Sandoval <osandov@fb.com> Cc: Kashyap Desai <kashyap.desai@broadcom.com> Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com> Cc: Ewan D. Milne <emilne@redhat.com> Tested-by: Sumanesh Samanta <sumanesh.samanta@broadcom.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'block/blk-mq.c')
-rw-r--r--block/blk-mq.c36
1 files changed, 25 insertions, 11 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2e8c94e00f58..2e825a7a3606 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1277,10 +1277,15 @@ static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
bool need_budget)
{
struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
+ int budget_token = -1;
- if (need_budget && !blk_mq_get_dispatch_budget(rq->q)) {
- blk_mq_put_driver_tag(rq);
- return PREP_DISPATCH_NO_BUDGET;
+ if (need_budget) {
+ budget_token = blk_mq_get_dispatch_budget(rq->q);
+ if (budget_token < 0) {
+ blk_mq_put_driver_tag(rq);
+ return PREP_DISPATCH_NO_BUDGET;
+ }
+ blk_mq_set_rq_budget_token(rq, budget_token);
}
if (!blk_mq_get_driver_tag(rq)) {
@@ -1297,7 +1302,7 @@ static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
* together during handling partial dispatch
*/
if (need_budget)
- blk_mq_put_dispatch_budget(rq->q);
+ blk_mq_put_dispatch_budget(rq->q, budget_token);
return PREP_DISPATCH_NO_TAG;
}
}
@@ -1307,12 +1312,16 @@ static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
/* release all allocated budgets before calling to blk_mq_dispatch_rq_list */
static void blk_mq_release_budgets(struct request_queue *q,
- unsigned int nr_budgets)
+ struct list_head *list)
{
- int i;
+ struct request *rq;
- for (i = 0; i < nr_budgets; i++)
- blk_mq_put_dispatch_budget(q);
+ list_for_each_entry(rq, list, queuelist) {
+ int budget_token = blk_mq_get_rq_budget_token(rq);
+
+ if (budget_token >= 0)
+ blk_mq_put_dispatch_budget(q, budget_token);
+ }
}
/*
@@ -1410,7 +1419,8 @@ out:
(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED);
bool no_budget_avail = prep == PREP_DISPATCH_NO_BUDGET;
- blk_mq_release_budgets(q, nr_budgets);
+ if (nr_budgets)
+ blk_mq_release_budgets(q, list);
spin_lock(&hctx->lock);
list_splice_tail_init(list, &hctx->dispatch);
@@ -2009,6 +2019,7 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
{
struct request_queue *q = rq->q;
bool run_queue = true;
+ int budget_token;
/*
* RCU or SRCU read lock is needed before checking quiesced flag.
@@ -2026,11 +2037,14 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
if (q->elevator && !bypass_insert)
goto insert;
- if (!blk_mq_get_dispatch_budget(q))
+ budget_token = blk_mq_get_dispatch_budget(q);
+ if (budget_token < 0)
goto insert;
+ blk_mq_set_rq_budget_token(rq, budget_token);
+
if (!blk_mq_get_driver_tag(rq)) {
- blk_mq_put_dispatch_budget(q);
+ blk_mq_put_dispatch_budget(q, budget_token);
goto insert;
}