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Date: Sat, 31 Jul 2021 15:13:22 +0800
From: "yukuai (C)" <yukuai3@...wei.com>
To: <axboe@...nel.dk>, <ming.lei@...hat.com>
CC: <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<yi.zhang@...wei.com>
Subject: Re: [PATCH] blk-mq: allow hardware queue to get more tag while
sharing a tag set
On 2021/07/20 20:33, yukuai (C) wrote:
> On 2021/07/12 11:18, Yu Kuai wrote:
>> If there are multiple active queues while sharing a tag set, it's not
>> necessary to limit the available tags as same share for each active queue
>> if no one ever failed to get driver tag. And fall back to same share if
>> someone do failed to get driver tag.
>>
>> This modification will be beneficial if total queue_depth of disks
>> on the same host is less than total tags.
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>> block/blk-mq-debugfs.c | 2 ++
>> block/blk-mq-tag.c | 43 +++++++++++++++++++++++++++++++++++++++++-
>> block/blk-mq-tag.h | 27 ++++++++++++++++++++++++--
>> block/blk-mq.c | 13 ++++++++++---
>> block/blk-mq.h | 8 ++++++++
>> include/linux/blk-mq.h | 4 ++++
>> include/linux/blkdev.h | 1 +
>> 7 files changed, 92 insertions(+), 6 deletions(-)
>>
>> diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
>> index 4b66d2776eda..35f1f01d93ae 100644
>> --- a/block/blk-mq-debugfs.c
>> +++ b/block/blk-mq-debugfs.c
>> @@ -450,6 +450,8 @@ static void blk_mq_debugfs_tags_show(struct
>> seq_file *m,
>> seq_printf(m, "nr_reserved_tags=%u\n", tags->nr_reserved_tags);
>> seq_printf(m, "active_queues=%d\n",
>> atomic_read(&tags->active_queues));
>> + seq_printf(m, "pending_queues=%d\n",
>> + atomic_read(&tags->pending_queues));
>> seq_puts(m, "\nbitmap_tags:\n");
>> sbitmap_queue_show(tags->bitmap_tags, m);
>> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
>> index 86f87346232a..618624b359d6 100644
>> --- a/block/blk-mq-tag.c
>> +++ b/block/blk-mq-tag.c
>> @@ -40,6 +40,22 @@ bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
>> return true;
>> }
>> +void __blk_mq_dtag_busy(struct blk_mq_hw_ctx *hctx)
>> +{
>> + if (blk_mq_is_sbitmap_shared(hctx->flags)) {
>> + struct request_queue *q = hctx->queue;
>> + struct blk_mq_tag_set *set = q->tag_set;
>> +
>> + if (!test_bit(QUEUE_FLAG_HCTX_WAIT, &q->queue_flags) &&
>> + !test_and_set_bit(QUEUE_FLAG_HCTX_WAIT, &q->queue_flags))
>> + atomic_inc(&set->pending_queues_shared_sbitmap);
>> + } else {
>> + if (!test_bit(BLK_MQ_S_DTAG_WAIT, &hctx->state) &&
>> + !test_and_set_bit(BLK_MQ_S_DTAG_WAIT, &hctx->state))
>> + atomic_inc(&hctx->tags->pending_queues);
>> + }
>> +}
>> +
>> /*
>> * Wakeup all potentially sleeping on tags
>> */
>> @@ -74,6 +90,24 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
>> blk_mq_tag_wakeup_all(tags, false);
>> }
>> +void __blk_mq_dtag_idle(struct blk_mq_hw_ctx *hctx)
>> +{
>> + struct blk_mq_tags *tags = hctx->tags;
>> + struct request_queue *q = hctx->queue;
>> + struct blk_mq_tag_set *set = q->tag_set;
>> +
>> + if (blk_mq_is_sbitmap_shared(hctx->flags)) {
>> + if (!test_and_clear_bit(QUEUE_FLAG_HCTX_WAIT,
>> + &q->queue_flags))
>> + return;
>> + atomic_dec(&set->pending_queues_shared_sbitmap);
>> + } else {
>> + if (!test_and_clear_bit(BLK_MQ_S_DTAG_WAIT, &hctx->state))
>> + return;
>> + atomic_dec(&tags->pending_queues);
>> + }
>> +}
>> +
>> static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
>> struct sbitmap_queue *bt)
>> {
>> @@ -112,8 +146,12 @@ unsigned int blk_mq_get_tag(struct
>> blk_mq_alloc_data *data)
>> if (tag != BLK_MQ_NO_TAG)
>> goto found_tag;
>> - if (data->flags & BLK_MQ_REQ_NOWAIT)
>> + if (data->flags & BLK_MQ_REQ_NOWAIT) {
>> + if (!data->q->elevator)
>> + blk_mq_dtag_busy(data->hctx);
>> +
>> return BLK_MQ_NO_TAG;
>> + }
>> ws = bt_wait_ptr(bt, data->hctx);
>> do {
>> @@ -140,6 +178,9 @@ unsigned int blk_mq_get_tag(struct
>> blk_mq_alloc_data *data)
>> if (tag != BLK_MQ_NO_TAG)
>> break;
>> + if (!data->q->elevator)
>> + blk_mq_dtag_busy(data->hctx);
>> +
>> bt_prev = bt;
>> io_schedule();
>> diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
>> index 8ed55af08427..badcf3693749 100644
>> --- a/block/blk-mq-tag.h
>> +++ b/block/blk-mq-tag.h
>> @@ -10,6 +10,11 @@ struct blk_mq_tags {
>> unsigned int nr_reserved_tags;
>> atomic_t active_queues;
>> + /*
>> + * if multiple queues share a tag set, pending_queues record the
>> + * number of queues that can't get driver tag.
>> + */
>> + atomic_t pending_queues;
>> struct sbitmap_queue *bitmap_tags;
>> struct sbitmap_queue *breserved_tags;
>> @@ -69,8 +74,10 @@ enum {
>> BLK_MQ_TAG_MAX = BLK_MQ_NO_TAG - 1,
>> };
>> -extern bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *);
>> -extern void __blk_mq_tag_idle(struct blk_mq_hw_ctx *);
>> +extern bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx);
>> +extern void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx);
>> +extern void __blk_mq_dtag_busy(struct blk_mq_hw_ctx *hctx);
>> +extern void __blk_mq_dtag_idle(struct blk_mq_hw_ctx *hctx);
>> static inline bool blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
>> {
>> @@ -88,6 +95,22 @@ static inline void blk_mq_tag_idle(struct
>> blk_mq_hw_ctx *hctx)
>> __blk_mq_tag_idle(hctx);
>> }
>> +static inline void blk_mq_dtag_busy(struct blk_mq_hw_ctx *hctx)
>> +{
>> + if (!(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED))
>> + return;
>> +
>> + __blk_mq_dtag_busy(hctx);
>> +}
>> +
>> +static inline void blk_mq_dtag_idle(struct blk_mq_hw_ctx *hctx)
>> +{
>> + if (!(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED))
>> + return;
>> +
>> + __blk_mq_dtag_idle(hctx);
>> +}
>> +
>> static inline bool blk_mq_tag_is_reserved(struct blk_mq_tags *tags,
>> unsigned int tag)
>> {
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 2c4ac51e54eb..1bb52bd71da8 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -991,8 +991,10 @@ static void blk_mq_timeout_work(struct
>> work_struct *work)
>> */
>> queue_for_each_hw_ctx(q, hctx, i) {
>> /* the hctx may be unmapped, so check it here */
>> - if (blk_mq_hw_queue_mapped(hctx))
>> + if (blk_mq_hw_queue_mapped(hctx)) {
>> blk_mq_tag_idle(hctx);
>> + blk_mq_dtag_idle(hctx);
>> + }
>> }
>> }
>> blk_queue_exit(q);
>> @@ -1097,8 +1099,10 @@ static bool __blk_mq_get_driver_tag(struct
>> request *rq)
>> }
>> tag = __sbitmap_queue_get(bt);
>> - if (tag == BLK_MQ_NO_TAG)
>> + if (tag == BLK_MQ_NO_TAG) {
>> + blk_mq_dtag_busy(rq->mq_hctx);
>> return false;
>> + }
>> rq->tag = tag + tag_offset;
>> return true;
>> @@ -2676,8 +2680,10 @@ static void blk_mq_exit_hctx(struct
>> request_queue *q,
>> {
>> struct request *flush_rq = hctx->fq->flush_rq;
>> - if (blk_mq_hw_queue_mapped(hctx))
>> + if (blk_mq_hw_queue_mapped(hctx)) {
>> blk_mq_tag_idle(hctx);
>> + blk_mq_dtag_idle(hctx);
>> + }
>> blk_mq_clear_flush_rq_mapping(set->tags[hctx_idx],
>> set->queue_depth, flush_rq);
>> @@ -3536,6 +3542,7 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set
>> *set)
>> if (blk_mq_is_sbitmap_shared(set->flags)) {
>> atomic_set(&set->active_queues_shared_sbitmap, 0);
>> + atomic_set(&set->pending_queues_shared_sbitmap, 0);
>> if (blk_mq_init_shared_sbitmap(set)) {
>> ret = -ENOMEM;
>> diff --git a/block/blk-mq.h b/block/blk-mq.h
>> index d08779f77a26..9e646ade81a8 100644
>> --- a/block/blk-mq.h
>> +++ b/block/blk-mq.h
>> @@ -337,10 +337,18 @@ static inline bool hctx_may_queue(struct
>> blk_mq_hw_ctx *hctx,
>> if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
>> return true;
>> +
>> + if (!atomic_read(&set->pending_queues_shared_sbitmap))
>> + return true;
>> +
>> users = atomic_read(&set->active_queues_shared_sbitmap);
>> } else {
>> if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
>> return true;
>> +
>> + if (!atomic_read(&hctx->tags->pending_queues))
>> + return true;
>> +
>> users = atomic_read(&hctx->tags->active_queues);
>> }
>> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
>> index 1d18447ebebc..3bc0faf0e2cf 100644
>> --- a/include/linux/blk-mq.h
>> +++ b/include/linux/blk-mq.h
>> @@ -256,6 +256,7 @@ struct blk_mq_tag_set {
>> unsigned int flags;
>> void *driver_data;
>> atomic_t active_queues_shared_sbitmap;
>> + atomic_t pending_queues_shared_sbitmap;
>> struct sbitmap_queue __bitmap_tags;
>> struct sbitmap_queue __breserved_tags;
>> @@ -415,6 +416,9 @@ enum {
>> /* hw queue is inactive after all its CPUs become offline */
>> BLK_MQ_S_INACTIVE = 3,
>> + /* hw queue is waiting for driver tag */
>> + BLK_MQ_S_DTAG_WAIT = 1,
>> +
>> BLK_MQ_MAX_DEPTH = 10240,
>> BLK_MQ_CPU_WORK_BATCH = 8,
>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>> index 3177181c4326..55e0965c9c3c 100644
>> --- a/include/linux/blkdev.h
>> +++ b/include/linux/blkdev.h
>> @@ -603,6 +603,7 @@ struct request_queue {
>> #define QUEUE_FLAG_RQ_ALLOC_TIME 27 /* record rq->alloc_time_ns */
>> #define QUEUE_FLAG_HCTX_ACTIVE 28 /* at least one blk-mq hctx
>> is active */
>> #define QUEUE_FLAG_NOWAIT 29 /* device supports NOWAIT */
>> +#define QUEUE_FLAG_HCTX_WAIT 30 /* at least one blk-mq hctx
>> can't get driver tag */
>> #define QUEUE_FLAG_MQ_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
>> (1 << QUEUE_FLAG_SAME_COMP) | \
>>
>
> ping ...
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