From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A31B3C54EE9 for ; Sat, 17 Sep 2022 15:06:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229519AbiIQPGt (ORCPT ); Sat, 17 Sep 2022 11:06:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36324 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229452AbiIQPGs (ORCPT ); Sat, 17 Sep 2022 11:06:48 -0400 Received: from out30-131.freemail.mail.aliyun.com (out30-131.freemail.mail.aliyun.com [115.124.30.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6DFD5303C7; Sat, 17 Sep 2022 08:06:45 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046059;MF=liusong@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0VQ.Efl4_1663427202; Received: from 30.39.244.121(mailfrom:liusong@linux.alibaba.com fp:SMTPD_---0VQ.Efl4_1663427202) by smtp.aliyun-inc.com; Sat, 17 Sep 2022 23:06:43 +0800 Message-ID: Date: Sat, 17 Sep 2022 23:06:41 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH] sbitmap: fix permanent io blocking caused by insufficient wakeup times To: Yu Kuai , axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, "yukuai (C)" References: <1663381981-6413-1-git-send-email-liusong@linux.alibaba.com> From: Liu Song In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 在 2022/9/17 18:20, Yu Kuai 写道: > Hi, > > 在 2022/09/17 10:33, Liu Song 写道: >> From: Liu Song >> >> 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 >> --- >>   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); >>   } >>