linux-kernel - Re: [PATCH v16 00/22] per memcg lru

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Date:   Sun, 19 Jul 2020 21:47:49 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Alex Shi <alex.shi@...ux.alibaba.com>
cc:     Hugh Dickins <hughd@...gle.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Tejun Heo <tj@...nel.org>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Matthew Wilcox <willy@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        kbuild test robot <lkp@...el.com>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, cgroups@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Wei Yang <richard.weiyang@...il.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>
Subject: Re: [PATCH v16 00/22] per memcg lru_lock

On Mon, 20 Jul 2020, Alex Shi wrote:
> 在 2020/7/19 下午11:23, Hugh Dickins 写道:
> > I noticed that 5.8-rc5, with lrulock v16 applied, took significantly
> > longer to run loads than without it applied, when there should have been
> > only slight differences in system time. Comparing /proc/vmstat, something
> > that stood out was "pgrotated 0" for the patched kernels, which led here:
> > 
> > If pagevec_lru_move_fn() is now to TestClearPageLRU (I have still not
> > decided whether that's good or not, but assume here that it is good),
> > then functions called though it must be changed not to expect PageLRU!
> > 
> > Signed-off-by: Hugh Dickins <hughd@...gle.com>
> 
> Good catch!
> 
> Thanks a lot, Hugh! 
> except 6 changes should apply, looks we add one more in swap.c file to stop
> !PageRLU further actions!

Agreed, that's a minor optimization that wasn't done before,
that can be added (but it's not a fix like the rest of them).

> 
> Many Thanks!
> Alex
> 
> @@ -649,7 +647,7 @@ void deactivate_file_page(struct page *page)
>          * In a workload with many unevictable page such as mprotect,
>          * unevictable page deactivation for accelerating reclaim is pointless.
>          */
> -       if (PageUnevictable(page))
> +       if (PageUnevictable(page) || !PageLRU(page))
>                 return;
> 
>         if (likely(get_page_unless_zero(page))) {