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Date:   Tue, 18 Oct 2022 00:46:24 +0200
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Tejun Heo <tj@kernel.org>
Cc:     Waiman Long <longman@redhat.com>, Michal Hocko <mhocko@suse.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Shakeel Butt <shakeelb@google.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        linux-mm@kvack.org, Chris Down <chris@chrisdown.name>
Subject: Re: [PATCH] mm/memcontrol: Don't increase effective low/min if no
 protection needed
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On Tue, Oct 11, 2022 at 07:04:32AM -1000, Tejun Heo <tj@kernel.org> wrote:
> Wouldn't it make sense to fix the test? With recursive_prot on, the cgroup
> actually is under low protection and it seems like the correct behavior is
> to report the low events accordingly.

It depends whether the there is a residual protection that the
memory.low=0 sibling can use (with memory_recursiveprot).

In the discussed LTP test, there should be no residual protection that
would justify the apparently misreported memory.low events. I.e. the
test is correct, the failure points to a subtle issue with distributing
residual protection among siblings.

Been there, (haven't) done that:
1) https://bugzilla.suse.com/show_bug.cgi?id=1196298
2) https://lore.kernel.org/r/20220325103118.GC2828@blackbody.suse.cz/

HTH,
Michal