Re: [PATCH 0/1] Add swappiness argument to memory.reclaim

Michal Hocko
2023-11-30T15:57:47Z

On Thu 30-11-23 07:36:53, Dan Schatzberg wrote:
[...]
> In contrast, I argue in favor of a swappiness setting not as a way to implement
> custom reclaim algorithms but rather to bias the balance of anon vs file due to
> differences of proactive vs reactive reclaim. In this context, swappiness is the
> existing interface for controlling this balance and this patch simply allows for
> it to be configured differently for proactive vs reactive reclaim.

I do agree that swappiness is a better interface than explicit anon/file
but the problem with swappiness is that it is more of a hint for the reclaim
rather than a real control. Just look at get_scan_count and its history.
Not only its range has been extended also the extent when it is actually
used has been changing all the time and I think it is not a stretch to
assume that trend to continue.

Now if we extend the user interface to trigger the reclaim do we expect
that we always do SCAN_EQUAL if a user specifies swappiness or are we OK
that the implementation is free to ignore that "hint"?
--
Michal Hocko
SUSE Labs