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From:   Muchun Song <songmuchun@bytedance.com>
Date:   Sun, 11 Apr 2021 13:37:26 +0800
Message-ID: <CAMZfGtVnmcuVqqg13pkL=72YwuyjVZDNE81-_d7S61e4a1kXGQ@mail.gmail.com>
Subject: Re: [External] Re: [RFC PATCH v2 04/18] mm: memcontrol: simplify lruvec_holds_page_lru_lock
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     guro@fb.com, mhocko@kernel.org, akpm@linux-foundation.org,
        shakeelb@google.com, vdavydov.dev@gmail.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        duanxiongchun@bytedance.com, fam.zheng@bytedance.com,
        bsingharora@gmail.com, shy828301@gmail.com,
        alex.shi@linux.alibaba.com
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On Sat, Apr 10, 2021 at 12:00 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Fri, Apr 09, 2021 at 08:29:45PM +0800, Muchun Song wrote:
> > We already have a helper lruvec_memcg() to get the memcg from lruvec, we
> > do not need to do it ourselves in the lruvec_holds_page_lru_lock(). So use
> > lruvec_memcg() instead. And if mem_cgroup_disabled() returns false, the
> > page_memcg(page) (the LRU pages) cannot be NULL. So remove the odd logic
> > of "memcg = page_memcg(page) ? : root_mem_cgroup". And use lruvec_pgdat
> > to simplify the code. We can have a single definition for this function
> > that works for !CONFIG_MEMCG, CONFIG_MEMCG + mem_cgroup_disabled() and
> > CONFIG_MEMCG.
> >
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>
> Looks good to me.
>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Thanks for your review.

>
> If you haven't done so yet, please make sure to explicitly test with
> all three config combinations, just because the dummy abstractions for
> memcg disabled or compiled out tend to be paper thin and don't always
> behave the way you might expect when you do more complicated things.

I have tested. There is no problem. Thanks :-)


>
> Something like
>
> boot
> echo sparsefile >/dev/null (> ram size to fill memory and reclaim)
> echo 1 >/proc/sys/vm/compact_memory
>
> should exercise this new function in a couple of important scenarios.