Re: [PATCH v4 1/1] mm: vmscan: Reduce throttling due to a failure to make progress

[Shakeel Butt]

On Fri, Dec 3, 2021 at 11:08 AM Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote:
>
[...]
> > 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?