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[115.124.30.131]) by mx.google.com with ESMTPS id 31si8215267plh.231.2019.05.10.09.50.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 10 May 2019 09:50:13 -0700 (PDT) Received-SPF: pass (google.com: domain of yang.shi@linux.alibaba.com designates 115.124.30.131 as permitted sender) client-ip=115.124.30.131; Authentication-Results: mx.google.com; spf=pass (google.com: domain of yang.shi@linux.alibaba.com designates 115.124.30.131 as permitted sender) smtp.mailfrom=yang.shi@linux.alibaba.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=alibaba.com X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04446;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0TRMJzjz_1557507007; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0TRMJzjz_1557507007) by smtp.aliyun-inc.com(127.0.0.1); Sat, 11 May 2019 00:50:10 +0800 Subject: Re: [PATCH] mm: vmscan: correct nr_reclaimed for THP To: Matthew Wilcox , "Huang, Ying" Cc: hannes@cmpxchg.org, mhocko@suse.com, mgorman@techsingularity.net, kirill.shutemov@linux.intel.com, hughd@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1557447392-61607-1-git-send-email-yang.shi@linux.alibaba.com> <87y33fjbvr.fsf@yhuang-dev.intel.com> <20190510163612.GA23417@bombadil.infradead.org> From: Yang Shi Message-ID: <3a919cba-fefe-d78e-313a-8f0d81a4a75d@linux.alibaba.com> Date: Fri, 10 May 2019 09:50:04 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20190510163612.GA23417@bombadil.infradead.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US 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 5/10/19 9:36 AM, Matthew Wilcox wrote: > On Fri, May 10, 2019 at 10:12:40AM +0800, Huang, Ying wrote: >>> + nr_reclaimed += (1 << compound_order(page)); >> How about to change this to >> >> >> nr_reclaimed += hpage_nr_pages(page); > Please don't. That embeds the knowledge that we can only swap out either > normal pages or THP sized pages. I'm trying to make the VM capable of > supporting arbitrary-order pages, and this would be just one more place > to fix. > > I'm sympathetic to the "self documenting" argument. My current tree has > a patch in it: > > mm: Introduce compound_nr > > Replace 1 << compound_order(page) with compound_nr(page). Minor > improvements in readability. > > It goes along with this patch: > > mm: Introduce page_size() > > It's unnecessarily hard to find out the size of a potentially huge page. > Replace 'PAGE_SIZE << compound_order(page)' with page_size(page). So you prefer keeping using  "1 << compound_order" as v1 did? Then you will convert all "1 << compound_order" to compound_nr? > > Better suggestions on naming gratefully received. I'm more happy with > page_size() than I am with compound_nr(). page_nr() gives the wrong > impression; page_count() isn't great either.