On Tue, Aug 16, 2022, at 11:25 AM, Nikolay Borisov wrote:

On 16.08.22 г. 17:22 ч., Chris Murphy wrote:

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On Sun, Aug 14, 2022, at 4:28 PM, Chris Murphy wrote:

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On Fri, Aug 12, 2022, at 2:02 PM, Jens Axboe wrote:

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Might be worth trying to revert those from 5.12 to see if they are
causing the issue? Jan, Paolo - does this ring any bells?

git log --oneline --no-merges v5.11..c03c21ba6f4e > bisect.txt

I tried checking out a33df75c6328, which is right before the first bfq
commit, but that kernel won't boot the hardware.

Next I checked out v5.12, then reverted these commits in order (that
they were found in the bisect.txt file):

7684fbde4516 bfq: Use only idle IO periods for think time calculations
28c6def00919 bfq: Use 'ttime' local variable
41e76c85660c bfq: Avoid false bfq queue merging

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a5bf0a92e1b8 bfq: bfq_check_waker() should be static

71217df39dc6 block, bfq: make waker-queue detection more robust
5a5436b98d5c block, bfq: save also injection state on queue merging
e673914d52f9 block, bfq: save also weight-raised service on queue merging
d1f600fa4732 block, bfq: fix switch back from soft-rt weitgh-raising
7f1995c27b19 block, bfq: re-evaluate convenience of I/O plugging on rq arrivals
eb2fd80f9d2c block, bfq: replace mechanism for evaluating I/O intensity

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1a23e06cdab2 bfq: don't duplicate code for different paths

2391d13ed484 block, bfq: do not expire a queue when it is the only busy
one
3c337690d2eb block, bfq: avoid spurious switches to soft_rt of
interactive queues
91b896f65d32 block, bfq: do not raise non-default weights
ab1fb47e33dc block, bfq: increase time window for waker detection
d4fc3640ff36 block, bfq: set next_rq to waker_bfqq->next_rq in waker
injection
b5f74ecacc31 block, bfq: use half slice_idle as a threshold to check
short ttime

The two commits prefixed by >>> above were not previously mentioned by
Jens, but I reverted them anyway because they showed up in the git log
command.

OK so, within 10 minutes the problem does happen still. This is
block/bfq-iosched.c resulting from the above reverts, in case anyone
wants to double check what I did:
https://drive.google.com/file/d/1ykU7MpmylJuXVobODWiiaLJk-XOiAjSt/view?usp=sharing

Any suggestions for further testing? I could try go down farther in the bisect.txt list. The problem is if the hardware falls over on an unbootable kernel, I have to bug someone with LOM access. That's a limited resource.

How about changing the scheduler either mq-deadline or noop, just to see 
if this is also reproducible with a different scheduler. I guess noop 
would imply the blk cgroup controller is going to be disabled

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.

-- 
Chris Murphy