Comment # 42 on bug 1159882 from Vlastimil Babka

(In reply to Michal Hocko from comment #41)
> Vlastimil, I remember we have discussed this problem in upstream some time
> ago. You've had a patch which has disabled the heuristic (2c012a4ad1a2).
> Testing with that reverted would sound like a good next step.

I think the past discussion was about us *not* having 2c012a4ad1a2 (in an older
kernel) as the problem was different - file pages thrashing while unused
anonymous pages sit idly. See
https://lore.kernel.org/linux-mm/b7f5e356-1f0a-98be-4a32-09a766c3949b@suse.cz/

Anyway, what is the actual observed issue here? Is it that part of the swap
gets used? I think Michal's analysis in comment 33 shows the swapped out pages
are not accessed (no increase in pswpin) so it shouldn't actually cause
excessive IO. So is it only that the swap being used looks bad?

If there's really observed performance issue (e.g. system being sluggish) while
doing the operations listed in comment 23, does disabling swap completely make
any difference? If not, we might be looking at a red flag here, IMHO.