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kyber: introduce kyber_depth_updated() 

Hang occurs when user changes the scheduler queue depth, by writing to
the 'nr_requests' sysfs file of that device.

The details of the environment that we found the problem are as follows:
  an eMMC block device
  total driver tags: 16
  default queue_depth: 32
  kqd->async_depth initialized in kyber_init_sched() with queue_depth=32

Then we change queue_depth to 256, by writing to the 'nr_requests' sysfs
file. But kqd->async_depth don't be updated after queue_depth changes.
Now the value of async depth is too small for queue_depth=256, this may
cause hang.

This patch introduces kyber_depth_updated(), so that kyber can update
async depth when queue depth changes.

Signed-off-by: Yang Yang <yang.yang@vivo.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Yang Yang 2021-02-05 01:13:10 -08:00 committed by Jens Axboe
parent 4ceddce55e
commit ffa772cfe9
1 changed files with 13 additions and 16 deletions
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29
block/kyber-iosched.c
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@ -355,19 +355,9 @@ static void kyber_timer_fn(struct timer_list *t)
}
}
static unsigned int kyber_sched_tags_shift(struct request_queue *q)
{
/*
* All of the hardware queues have the same depth, so we can just grab
* the shift of the first one.
*/
return q->queue_hw_ctx[0]->sched_tags->bitmap_tags->sb.shift;
}
static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
{
struct kyber_queue_data *kqd;
unsigned int shift;
int ret = -ENOMEM;
int i;
@ -402,9 +392,6 @@ static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
kqd->latency_targets[i] = kyber_latency_targets[i];
}
shift = kyber_sched_tags_shift(q);
kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
return kqd;
err_buckets:
@ -460,9 +447,19 @@ static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq)
INIT_LIST_HEAD(&kcq->rq_list[i]);
}
static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx)
{
struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
struct blk_mq_tags *tags = hctx->sched_tags;
unsigned int shift = tags->bitmap_tags->sb.shift;
kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
sbitmap_queue_min_shallow_depth(tags->bitmap_tags, kqd->async_depth);
}
static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
{
struct kyber_hctx_data *khd;
int i;
@ -504,8 +501,7 @@ static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
khd->batching = 0;
hctx->sched_data = khd;
sbitmap_queue_min_shallow_depth(hctx->sched_tags->bitmap_tags,
kqd->async_depth);
kyber_depth_updated(hctx);
return 0;
@ -1024,6 +1020,7 @@ static struct elevator_type kyber_sched = {
.completed_request = kyber_completed_request,
.dispatch_request = kyber_dispatch_request,
.has_work = kyber_has_work,
.depth_updated = kyber_depth_updated,
},
#ifdef CONFIG_BLK_DEBUG_FS
.queue_debugfs_attrs = kyber_queue_debugfs_attrs,