From f95c93db8bf2b17bee124466d0ff1bab18948627 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Wed, 10 May 2023 09:32:41 -0700 Subject: [PATCH] ANDROID: block: Improve shared tag set performance Remove the code for fair tag sharing because it significantly hurts performance for UFS devices. Removing this code is safe because the legacy block layer worked fine without any equivalent fairness algorithm. This algorithm hurts performance for UFS devices because UFS devices have multiple logical units. One of these logical units (WLUN) is used to submit control commands, e.g. START STOP UNIT. If any request is submitted to the WLUN, the queue depth is reduced from 31 to 15 or lower for data LUNs. See also https://lore.kernel.org/linux-scsi/20221229030645.11558-1-ed.tsai@mediatek.com/ Cc: Christoph Hellwig Cc: Martin K. Petersen Cc: Ming Lei Cc: Keith Busch Cc: Damien Le Moal Cc: Ed Tsai Change-Id: Ia6d75917d533f32fffc68348b52fd3d972c9074c Signed-off-by: Bart Van Assche Bug: 281845090 Bug: 307790116 Bug: 390523143 Link: https://lore.kernel.org/linux-block/20230103195337.158625-1-bvanassche@acm.org/ Signed-off-by: Bart Van Assche (cherry picked from commit 12a703a56f1b01d295a7ee92e931daa56727620f) --- block/blk-mq-tag.c | 4 ---- block/blk-mq.c | 3 --- block/blk-mq.h | 39 --------------------------------------- 3 files changed, 46 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 2cafcf11ee8b..2b74489ccdc6 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -106,10 +106,6 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx) static int __blk_mq_get_tag(struct blk_mq_alloc_data *data, struct sbitmap_queue *bt) { - if (!data->q->elevator && !(data->flags & BLK_MQ_REQ_RESERVED) && - !hctx_may_queue(data->hctx, bt)) - return BLK_MQ_NO_TAG; - if (data->shallow_depth) return sbitmap_queue_get_shallow(bt, data->shallow_depth); else diff --git a/block/blk-mq.c b/block/blk-mq.c index 4e76651e786d..1ec5cb5ddf83 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1837,9 +1837,6 @@ bool __blk_mq_alloc_driver_tag(struct request *rq) if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag)) { bt = &rq->mq_hctx->tags->breserved_tags; tag_offset = 0; - } else { - if (!hctx_may_queue(rq->mq_hctx, bt)) - return false; } tag = __sbitmap_queue_get(bt); diff --git a/block/blk-mq.h b/block/blk-mq.h index f4ac1af77a26..acd947f5ff42 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -391,45 +391,6 @@ static inline void blk_mq_free_requests(struct list_head *list) } } -/* - * For shared tag users, we track the number of currently active users - * and attempt to provide a fair share of the tag depth for each of them. - */ -static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx, - struct sbitmap_queue *bt) -{ - unsigned int depth, users; - - if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) - return true; - - /* - * Don't try dividing an ant - */ - if (bt->sb.depth == 1) - return true; - - if (blk_mq_is_shared_tags(hctx->flags)) { - struct request_queue *q = hctx->queue; - - if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags)) - return true; - } else { - if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state)) - return true; - } - - users = READ_ONCE(hctx->tags->active_queues); - if (!users) - return true; - - /* - * Allow at least some tags - */ - depth = max((bt->sb.depth + users - 1) / users, 4U); - return __blk_mq_active_requests(hctx) < depth; -} - /* run the code block in @dispatch_ops with rcu/srcu read lock held */ #define __blk_mq_run_dispatch_ops(q, check_sleep, dispatch_ops) \ do { \