linux-kernel - Re: [PATCH v10] mm: vmscan: try to reclaim swapcache pages if no swap space

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Message-ID: <87h6l77wl5.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Mon, 27 Nov 2023 10:34:46 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Yosry Ahmed <yosryahmed@...gle.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Yu Zhao <yuzhao@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sachin Sant <sachinp@...ux.ibm.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Kefeng Wang <wangkefeng.wang@...wei.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10] mm: vmscan: try to reclaim swapcache pages if no
 swap space

Michal Hocko <mhocko@...e.com> writes:

> On Thu 23-11-23 14:15:59, Huang, Ying wrote:
>> Michal Hocko <mhocko@...e.com> writes:
> [...]
>> > Yes swapcache pages are indeed more complicated but most of the time
>> > they just go away as well, no?
>> 
>> When we swapin a page, we will put it in swapcache too.  And the page
>> can be in that state for long time if there is more than 50% free space
>> in the swap device.
>
> True, but why is that a problem? If you encounter such a swapped in page
> on the file LRU then the page should be referened and as such should be
> activated, no?

This just means that anonymous pages in file LRU aren't temporary or
short-term.  So we need to consider that.  For example, the original
method to balance between anonymous pages and file pages need to be
re-designed.  The anonymous pages are considered hotter than file pages
in general.

--
Best Regards,
Huang, Ying