On Fri, Dec 3, 2021 at 11:08 AM Mel Gorman [off-list ref] wrote:

[...]

quoted

I am in agreement with the motivation of the whole series. I am just
making sure that the motivation of VMSCAN_THROTTLE_NOPROGRESS based
throttle is more than just the congestion_wait of
mem_cgroup_force_empty_write.

The commit that primarily targets congestion_wait is 8cd7c588decf
("mm/vmscan: throttle reclaim until some writeback completes if
congested"). The series recognises that there are other reasons why
reclaim can fail to make progress that is not directly writeback related.

I agree with throttling for VMSCAN_THROTTLE_[WRITEBACK|ISOLATED]
reasons. Please explain why we should throttle for
VMSCAN_THROTTLE_NOPROGRESS? Also 69392a403f49 claims "Direct reclaim
primarily is throttled in the page allocator if it is failing to make
progress.", can you please explain how?