Messages in this thread | | | Date | Sat, 17 Sep 2022 23:06:41 +0800 | Subject | Re: [PATCH] sbitmap: fix permanent io blocking caused by insufficient wakeup times | From | Liu Song <> |
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在 2022/9/17 18:20, Yu Kuai 写道: > Hi, > > 在 2022/09/17 10:33, Liu Song 写道: >> From: Liu Song <liusong@linux.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? > Hi
It's a bit embarrassing. My code is 6.0-rc3. Yesterday, there was a problem with the Tsinghua mirror station. The fetched code could not be the latest, so I submitted it. According to your suggestion, I checked and it has been fixed, thank you for your suggestion.
Thanks
> Thanks, > Kuai >> Signed-off-by: Liu Song <liusong@linux.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); >> } >>
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