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[2003:cb:c701:9d00:ff87:1c9b:108a:9702]) by smtp.gmail.com with ESMTPSA id i12sm3055057wrf.100.2022.01.14.10.47.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 Jan 2022 10:47:49 -0800 (PST) Message-ID: <51fc9dfe-1cac-69f6-0c68-46a83fd7783d@redhat.com> Date: Fri, 14 Jan 2022 19:47:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [RFC v2] mm: introduce page pin owner From: David Hildenbrand To: Minchan Kim Cc: Andrew Morton , Michal Hocko , linux-mm , LKML , Suren Baghdasaryan , John Dias , huww98@outlook.com, John Hubbard References: <20211228175904.3739751-1-minchan@kernel.org> <35d7f27c-44e3-3921-c8d3-b6dee3b01238@redhat.com> <8f02e71b-5de7-4342-7371-a7fe19b114b5@redhat.com> Organization: Red Hat In-Reply-To: <8f02e71b-5de7-4342-7371-a7fe19b114b5@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: BA319160002 X-Stat-Signature: rfs99kpqn4wj6whpetptxq618egxpwee Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=B94H6j4w; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf08.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com X-Rspamd-Server: rspam02 X-HE-Tag: 1642186075-476029 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000020, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: >>>>>> Otherwise, I'd like to have feature naming more higher level>>>>>> to represent page migration failure and then tracking unref of >>>>>> the page. In the sense, PagePinOwner John suggested was good >>>>>> candidate(Even, my original naming PagePinner was worse) since >>>>> >>>>> Personally, I dislike both variants. >>>>> >>>>>> I was trouble to abstract the feature with short word. >>>>>> If we approach "what feature is doing" rather than "what's >>>>>> the feature's goal"(I feel the your suggestion would be close >>>>>> to what feature is doing), I'd like to express "unreference on >>>>>> migraiton failed page" so PAGE_EXT_UNMIGRATED_UNREF >>>>>> (However, I prefer the feature naming more "what we want to achieve") >>>>>> >>>>> E.g., PAGE_EXT_TRACE_UNREF will trace unref to the page once the bit is >>>>> set. The functionality itself is completely independent of migration >>>>> failures. That's just the code that sets it to enable the underlying >>>>> tracing for that specific page. >>>> >>>> I agree that make something general is great but I also want to avoid >>>> create something too big from the beginning with just imagination. >>>> So, I'd like to hear more concrete and appealing usecases and then >>>> we could think over this trace approach is really the best one to >>>> achieve the goal. Once it's agreed, the naming you suggested would >>>> make sense. >>> >>> At least for me it's a lot cleaner if a feature clearly expresses what >>> it actually does. Staring at PAGE_EXT_PIN_OWNER I initially had no clue. >>> I was assuming we would actually track (not trace!) all active FOLL_PIN >>> (not unref callers!). Maybe that makes it clearer why I'd prefer a >>> clearer name. >> >> I totally agree PagePinOwner is not 100% straightforward. I'm open for >> other better name. Currently we are discussing how we could generalize >> and whether it's useful or not. Depending on the discussion, the design/ >> interface as well as naming could be changed. No problem. > > PagePinOwner is just highly misleading. Because that's not what the > feature does. Having that said, i hope we'll get other opinions as well. FWIW, I think "page reference holder" would be clearer. PageRefHolder or PageReferenceHolder "Trace page reference holders on unref after migration of a page failed." -- Thanks, David / dhildenb