[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ab451e4c-e1ca-d7a3-6e02-c7d12a473124@huaweicloud.com>
Date: Sat, 17 Sep 2022 18:20:30 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Liu Song <liusong@...ux.alibaba.com>, axboe@...nel.dk
Cc: linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
"yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] sbitmap: fix permanent io blocking caused by insufficient
wakeup times
Hi,
在 2022/09/17 10:33, Liu Song 写道:
> From: Liu Song <liusong@...ux.alibaba.com>
>
> In "sbitmap_queue_clear_batch", a batch of completed requests may be
> processed at once, but "wait_cnt" is only reduced once by
> "sbitmap_queue_wake_up".
> In our environment, if "/sys/block/nvme0n1/nr_requests" is adjusted to
> 32, it is easily because no tag and then enter the waiting situation,
> if continue change "nr_requests" to 1023 at this time, it will basically
> fall into the situation of permanent blocking. Because there will be
> "blk_freeze_queue" in "blk_mq_update_nr_requests", which will prevent
> any new requests, but due to insufficient wake-up, there are tasks
> waiting for wake-up, but no new wake-up opportunities will be generated
> at this time, so this situation needs to be repaired.
>
It seems Keith already fixed this recently. Can you have a check at his
patch?
Thanks,
Kuai
> Signed-off-by: Liu Song <liusong@...ux.alibaba.com>
> ---
> include/linux/sbitmap.h | 8 ++++++++
> lib/sbitmap.c | 22 ++++++++++++++++++----
> 2 files changed, 26 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
> index 8f5a86e..153382e 100644
> --- a/include/linux/sbitmap.h
> +++ b/include/linux/sbitmap.h
> @@ -579,6 +579,14 @@ static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq,
> void sbitmap_queue_wake_up(struct sbitmap_queue *sbq);
>
> /**
> + * sbitmap_queue_wake_up_batch() - Attempt to wake up waiters in batches
> + * on a &struct sbitmap_queue.
> + * @sbq: Bitmap queue to wake up.
> + * @nr: The number of attempts to wake the waiter.
> + */
> +void sbitmap_queue_wake_up_batch(struct sbitmap_queue *sbq, int nr);
> +
> +/**
> * sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct
> * seq_file.
> * @sbq: Bitmap queue to show.
> diff --git a/lib/sbitmap.c b/lib/sbitmap.c
> index 29eb048..f2aa1da 100644
> --- a/lib/sbitmap.c
> +++ b/lib/sbitmap.c
> @@ -600,7 +600,7 @@ static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
> return NULL;
> }
>
> -static bool __sbq_wake_up(struct sbitmap_queue *sbq)
> +static bool __sbq_wake_up(struct sbitmap_queue *sbq, int *nr)
> {
> struct sbq_wait_state *ws;
> unsigned int wake_batch;
> @@ -610,6 +610,7 @@ static bool __sbq_wake_up(struct sbitmap_queue *sbq)
> if (!ws)
> return false;
>
> +again:
> wait_cnt = atomic_dec_return(&ws->wait_cnt);
> if (wait_cnt <= 0) {
> int ret;
> @@ -632,10 +633,14 @@ static bool __sbq_wake_up(struct sbitmap_queue *sbq)
> if (ret == wait_cnt) {
> sbq_index_atomic_inc(&sbq->wake_index);
> wake_up_nr(&ws->wait, wake_batch);
> - return false;
> + if (!nr || *nr <= 0)
> + return false;
> }
>
> return true;
> + } else if (nr && *nr) {
> + (*nr)--;
> + goto again;
> }
>
> return false;
> @@ -643,11 +648,20 @@ static bool __sbq_wake_up(struct sbitmap_queue *sbq)
>
> void sbitmap_queue_wake_up(struct sbitmap_queue *sbq)
> {
> - while (__sbq_wake_up(sbq))
> + while (__sbq_wake_up(sbq, NULL))
> ;
> }
> EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);
>
> +void sbitmap_queue_wake_up_batch(struct sbitmap_queue *sbq, int nr)
> +{
> + int i = SBQ_WAIT_QUEUES;
> +
> + while (__sbq_wake_up(sbq, &nr) && --i)
> + ;
> +}
> +EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up_batch);
> +
> static inline void sbitmap_update_cpu_hint(struct sbitmap *sb, int cpu, int tag)
> {
> if (likely(!sb->round_robin && tag < sb->depth))
> @@ -683,7 +697,7 @@ void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset,
> atomic_long_andnot(mask, (atomic_long_t *) addr);
>
> smp_mb__after_atomic();
> - sbitmap_queue_wake_up(sbq);
> + sbitmap_queue_wake_up_batch(sbq, nr_tags);
> sbitmap_update_cpu_hint(&sbq->sb, raw_smp_processor_id(),
> tags[nr_tags - 1] - offset);
> }
>
Powered by blists - more mailing lists