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From:   Jianlin Lv <iecedge@gmail.com>
Date:   Sun, 8 Oct 2023 17:34:44 +0800
Message-ID: <CAFA-uR9n-rKw4k26Bhm=P16jOMtAncRsno7o=yYJ1kTxmB_mRw@mail.gmail.com>
Subject: Re: [PATCH] memcg: add interface to force disable swap
To:     "Huang, Ying" <ying.huang@intel.com>
Cc:     tj@kernel.org, lizefan.x@bytedance.com, hannes@cmpxchg.org,
        corbet@lwn.net, mhocko@kernel.org, roman.gushchin@linux.dev,
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On Sun, Oct 8, 2023 at 4:26=E2=80=AFPM Huang, Ying <ying.huang@intel.com> w=
rote:
>
> Jianlin Lv <iecedge@gmail.com> writes:
>
> > On Sun, Oct 8, 2023 at 9:17=E2=80=AFAM Huang, Ying <ying.huang@intel.co=
m> wrote:
> >>
> >> Jianlin Lv <iecedge@gmail.com> writes:
> >>
> >> > From: Jianlin Lv <iecedge@gmail.com>
> >> >
> >> > 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 progr=
am.
> > Not sure whether this program can reproduce the issue in any environmen=
t.
> >
> > 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 introduce=
s
> > uncertainty.
> >
> > For the JVM issue at hand, we expect deterministic SCAN_FILE scan to av=
oid
> > 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