linux-kernel - Re: [RFC][PATCH 7/9] mm/vmscan: Consider anonymous pages without swap

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Date:   Thu, 29 Oct 2020 08:57:32 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Oscar Salvador <osalvador@...e.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>, kbusch@...nel.org,
        "Verma, Vishal L" <vishal.l.verma@...el.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        David Rientjes <rientjes@...gle.com>,
        Huang Ying <ying.huang@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Hildenbrand <david@...hat.com>
Subject: Re: [RFC][PATCH 7/9] mm/vmscan: Consider anonymous pages without swap

On Thu, Oct 29, 2020 at 7:33 AM Dave Hansen <dave.hansen@...el.com> wrote:
>
> On 10/29/20 1:14 AM, Oscar Salvador wrote:
> > With this patch, we will use always the atomic version
> > get_nr_swap_pages from now on. Is that ok? I guess so, but it might
> > warrant a mention in the changelog?
>
> I _think_ it's OK.  But, you're right that it's a potential behavior
> change that's not mentioned in the changelog.
>
> I'll mention it in the changelog and see if I can dream up any other
> practical implications from this change.

IMHO, we don't have to modify those two places at all. They are used
to rebalance the anon lru active/inactive ratio even if we did not try
to evict anon pages at all, so "total_swap_pages" is used instead of
checking swappiness and available swap space.

The changes may result in imbalanced anon lru.

>
> Thanks for taking a look!
>