Re: [PATCH] memcg: add interface to force disable swap

[Jianlin Lv]

On Sun, Oct 8, 2023 at 4:26 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>
> Jianlin Lv <iecedge@xxxxxxxxx> writes:
>
> > On Sun, Oct 8, 2023 at 9:17 AM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
> >>
> >> Jianlin Lv <iecedge@xxxxxxxxx> writes:
> >>
> >> > From: Jianlin Lv <iecedge@xxxxxxxxx>
> >> >
> >> > Global reclaim will swap even if swappiness is set to 0.
> >>
> >> Why?  Can you elaborate the situation?
> >
> > We reproduced the issue of pages being swapped out even when swappiness is
> > set to 0 in the production environment through the following test program.
> > Not sure whether this program can reproduce the issue in any environment.
> >
> > From the implementation of the get_scan_count code, it can be seen that,
> > based on the current runtime situation, memory reclamation will choose a
> > scanning method (SCAN_ANON/SCAN_FILE/SCAN_FRACT) to determine how
> > aggressively the anon and file LRU are scanned. However, this introduces
> > uncertainty.
> >
> > For the JVM issue at hand, we expect deterministic SCAN_FILE scan to avoid
> > swapping out anon pages.
>
> Why doesn't memory.swap.max work?

The main reason is that deployed nodes  are kept on cgroups v1.

>
> --
> Best Regards,
> Huang, Ying