Re: [REGRESSION] workqueue/writeback: Severe CPU hang due to kworker proliferation during I/O flush and cgroup cleanup

cc'ing GKE folks

On Fri, Sep 26, 2025 at 12:59 PM Tejun Heo tj@kernel.org wrote:

cc'ing Jan.

On Fri, Sep 26, 2025 at 12:54:29PM -0700, Chenglong Tang wrote:

...

Just did more testing here. Confirmed that the system hang's still there but less frequently(6/40) with the patches http://lkml.kernel.org/r/20250912103522.2935-1-jack@suse.cz appied to v6.17-rc7. In the bad instances, the kworker count climbed to over 600+ and caused the hang over 80+ seconds.

So I think the patches didn't fully solve the issue.

I wonder how the number of workers still exploded to 600+. Are there that many cgroups being shut down? Does clamping down @max_active resolve the problem? There's no reason to have really high concurrency for this.

Thanks.

-- tejun