Re: [PATCH v4 1/1] mm: vmscan: Reduce throttling due to a failure to make progress
From: Mel Gorman <hidden>
Date: 2021-12-06 11:25:51
Also in:
linux-fsdevel, lkml, regressions
On Sun, Dec 05, 2021 at 10:06:27PM -0800, Shakeel Butt wrote:
On Fri, Dec 3, 2021 at 11:08 AM Mel Gorman [off-list ref] wrote:quoted
[...]quoted
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?
It could happen if the pages on the LRU are being reactivated continually or holding an elevated reference count for some reason (e.g. gup, page migration etc). The event is probably transient, hence the short throttling. -- Mel Gorman SUSE Labs