linux-kernel - Re: stalling IO regression in linux 5.12

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Date:   Wed, 10 Aug 2022 15:31:38 -0400
From:   Josef Bacik <josef@...icpanda.com>
To:     Chris Murphy <lists@...orremedies.com>
Cc:     Btrfs BTRFS <linux-btrfs@...r.kernel.org>,
        Linux-RAID <linux-raid@...r.kernel.org>,
        linux-block@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: stalling IO regression in linux 5.12

On Wed, Aug 10, 2022 at 02:42:40PM -0400, Chris Murphy wrote:
> 
> 
> On Wed, Aug 10, 2022, at 2:33 PM, Chris Murphy wrote:
> > On Wed, Aug 10, 2022, at 1:48 PM, Josef Bacik wrote:
> >
> >> To help narrow this down can you disable any IO controller you've got enabled
> >> and see if you can reproduce?  If you can sysrq+w is super helpful as it'll
> >> point us in the next direction to look.  Thanks,
> >
> > I'm not following, sorry. I can boot with 
> > systemd.unified_cgroup_hierarchy=0 to make sure it's all off, but we're 
> > not using an IO cgroup controllers specifically as far as I'm aware.
> 
> OK yeah that won't work because the workload requires cgroup2 or it won't run.
>

Oh no I don't want cgroups completley off, just disable the io controller, so
figure out which cgroup your thing is being run in, and then

echo "-io" > <parent dir>/cgroup.subtree_control

If you cat /sys/fs/cgroup/whatever/cgroup/cgroup.controllers and you see "io" in
there keep doing the above in the next highest parent directory until io is no
longer in there.  Thanks,

Josef