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

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Date:   Wed, 22 Nov 2023 14:41:21 +0800
From:   Liu Shixin <liushixin2@...wei.com>
To:     Michal Hocko <mhocko@...e.com>
CC:     Yu Zhao <yuzhao@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yosry Ahmed <yosryahmed@...gle.com>,
        Huang Ying <ying.huang@...el.com>,
        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


On 2023/11/21 21:00, Michal Hocko wrote:
> On Tue 21-11-23 17:06:24, Liu Shixin wrote:
>
> However, in swapcache_only mode, the scan count still increased when scan
> non-swapcache pages because there are large number of non-swapcache pages
> and rare swapcache pages in swapcache_only mode, and if the non-swapcache
> is skipped and do not count, the scan of pages in isolate_lru_folios() can
> eventually lead to hung task, just as Sachin reported [2].
> I find this paragraph really confusing! I guess what you meant to say is
> that a real swapcache_only is problematic because it can end up not
> making any progress, correct? 
This paragraph is going to explain why checking swapcache_only after scan += nr_pages;
>
> AFAIU you have addressed that problem by making swapcache_only anon LRU
> specific, right? That would be certainly more robust as you can still
> reclaim from file LRUs. I cannot say I like that because swapcache_only
> is a bit confusing and I do not think we want to grow more special
> purpose reclaim types. Would it be possible/reasonable to instead put
> swapcache pages on the file LRU instead?
It looks like a good idea, but I'm not sure if it's possible. I can try it, is there anything to
pay attention to?

Thanks,