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

[Huang, Ying]

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?

--
Best Regards,
Huang, Ying