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[37.188.130.62]) by smtp.gmail.com with ESMTPSA id u74sm2906460wmu.13.2020.04.28.03.43.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Apr 2020 03:43:01 -0700 (PDT) Date: Tue, 28 Apr 2020 12:43:00 +0200 From: Michal Hocko To: Yafang Shao Cc: Johannes Weiner , Andrew Morton , Roman Gushchin , Chris Down , Linux MM Subject: Re: [PATCH 0/3] mm: improve proportional memcg protection Message-ID: <20200428104300.GN28637@dhcp22.suse.cz> References: <20200425152418.28388-1-laoar.shao@gmail.com> <20200427170540.GB29022@cmpxchg.org> <20200428080525.GL28637@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue 28-04-20 16:22:46, Yafang Shao wrote: > On Tue, Apr 28, 2020 at 4:05 PM Michal Hocko wrote: > > > > On Tue 28-04-20 09:45:27, Yafang Shao wrote: > > [...] > > > Seems we can't get an agreement on how to improve current code. > > > So I will submit a patch to revert the commit 9783aa9917f8 ("mm, > > > memcg: proportional memory.{low,min} reclaim") first. > > > > My current understanding is that the issue we are discussing here is > > mostly theoretical. Your changelog doesn't really talk about any real > > life workloads that would be suffering. > > Is real life workload really important ? It is really important to make cost vs. benefit decisions. Like whether to rever the said commit or not. > If so, why an issue[1] occured in the real workload report by me in > 2019 that memcg proection can't protect inactive pages (inodes) is > ignored again and again ? I do not think it is ignored. IIRC there was not an agreement on the way to fix this. I could get involved very much because there were other higher priority things to take care. People are simply busy. > So I'm questioning that what is the real life workload ? It is a workload which does something useful for their users. [...] > > So it would be really more helpful to not insist on unrelated > > implementation details and focus on two things 1) split up the effective > > values calculation from the predicate (cleanup without any functional > > changes) 2) make the calculation more robust against racing reclaimers. > > > > Another thing should be considered as well, 0) don't access > memroy.emin and elow in get_scan_count(). If you can achieve the gradual transition over protections by other means then I am really interested in more details. -- Michal Hocko SUSE Labs