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From:   "Huang, Ying" <ying.huang@intel.com>
To:     Michal Hocko <mhocko@suse.com>
Cc:     Yosry Ahmed <yosryahmed@google.com>,
        Liu Shixin <liushixin2@huawei.com>,
        Yu Zhao <yuzhao@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Sachin Sant <sachinp@linux.ibm.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Kefeng Wang <wangkefeng.wang@huawei.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v10] mm: vmscan: try to reclaim swapcache pages if no
 swap space
In-Reply-To: <ZWDPuR5Ssx07nBHb@tiehlicka> (Michal Hocko's message of "Fri, 24
        Nov 2023 17:30:49 +0100")
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        <32fe518a-e962-14ae-badc-719390386db9@huawei.com>
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Date:   Mon, 27 Nov 2023 10:34:46 +0800
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Michal Hocko <mhocko@suse.com> writes:

> On Thu 23-11-23 14:15:59, Huang, Ying wrote:
>> Michal Hocko <mhocko@suse.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