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From:   Ming Lei <ming.lei@redhat.com>
Date:   Wed, 17 Aug 2022 20:06:51 +0800
Message-ID: <CAFj5m9+6Vj3NdSg_n3nw1icscY1qr9f9SOvkWYyqpEtFBb_-1g@mail.gmail.com>
Subject: Re: stalling IO regression since linux 5.12, through 5.18
To:     Chris Murphy <lists@colorremedies.com>
Cc:     Nikolay Borisov <nborisov@suse.com>, Jens Axboe <axboe@kernel.dk>,
        Jan Kara <jack@suse.cz>,
        Paolo Valente <paolo.valente@linaro.org>,
        Btrfs BTRFS <linux-btrfs@vger.kernel.org>,
        Linux-RAID <linux-raid@vger.kernel.org>,
        linux-block <linux-block@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Josef Bacik <josef@toxicpanda.com>,
        Ming Lei <ming.lei@redhat.com>
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Hello Chris,

On Tue, Aug 16, 2022 at 11:35 PM Chris Murphy <lists@colorremedies.com> wrote:
>
>
>
...
>
> I already reported on that: always happens with bfq within an hour or less. Doesn't happen with mq-deadline for ~25+ hours. Does happen with bfq with the above patches removed. Does happen with cgroup.disabled=io set.
>
> Sounds to me like it's something bfq depends on and is somehow becoming perturbed in a way that mq-deadline does not, and has changed between 5.11 and 5.12. I have no idea what's under bfq that matches this description.
>

blk-mq debugfs log is usually helpful for io stall issue, care to post
the blk-mq debugfs log:

(cd /sys/kernel/debug/block/$disk && find . -type f -exec grep -aH . {} \;)

Thanks,
Ming