Re: [RFC PATCH 0/5] Remove dependency on congestion_wait in mm/

[Matthew Wilcox]

On Mon, Sep 20, 2021 at 09:54:31AM +0100, Mel Gorman wrote:
> This has been lightly tested only and the testing was useless as the
> relevant code was not executed. The workload configurations I had that
> used to trigger these corner cases no longer work (yey?) and I'll need
> to implement a new synthetic workload. If someone is aware of a realistic
> workload that forces reclaim activity to the point where reclaim stalls
> then kindly share the details.

The stereeotypical "stalling on I/O" problem is to plug in one of the
crap USB drives you were given at a trade show and simply
	dd if=/dev/zero of=/dev/sdb
	sync

You can also set up qemu to have extremely slow I/O performance:
https://serverfault.com/questions/675704/extremely-slow-qemu-storage-performance-with-qcow2-images