Re: [PATCH] mm, memcg: fix wrong mem cgroup protection

From: Chris Down <chris@chrisdown.name>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@kernel.org>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Linux MM <linux-mm@kvack.org>, Roman Gushchin <guro@fb.com>,
	stable@vger.kernel.org, Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH] mm, memcg: fix wrong mem cgroup protection
Date: Fri, 24 Apr 2020 13:18:36 +0100	[thread overview]
Message-ID: <20200424121836.GA1379200@chrisdown.name> (raw)
In-Reply-To: <CALOAHbDpvRZWcaoKBs2ywJFSY0MXT-WEe6wZTR=ed4-85Ovcgg@mail.gmail.com>

Yafang Shao writes:
>If the author can't understand deeply in the code worte by
>himself/herself, I think the author should do more test on his/her
>patches.
>Regarding the issue in this case, my understanding is you know the
>benefit of proportional reclaim, but I'm wondering that do you know
>the loss if the proportional is not correct ?
>I don't mean to affend you, while I just try to explain how the
>community should cooperate.

I'm pretty sure that since multiple people on mm list have already expressed 
confusion at this patch, this isn't a question of testing, but of lack of 
clarity in usage :-)

Promoting "testing" as a panacea for this issue misses a significant part of 
the real problem: that the intended semantics and room for allowed races is 
currently unclear, which is why there is a general sense of confusion around 
your proposed patch and what it solves. If more testing would help, then the 
benefit of your patch should be patently obvious -- but it isn't.