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(p200300cbc74c4500a7ddabc0e4c24b31.dip0.t-ipconnect.de. [2003:cb:c74c:4500:a7dd:abc0:e4c2:4b31]) by smtp.gmail.com with ESMTPSA id p20-20020a1c7414000000b003fe215e4492sm13146195wmc.4.2023.08.08.02.01.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Aug 2023 02:01:20 -0700 (PDT) Message-ID: Date: Tue, 8 Aug 2023 11:01:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v2 5/7] mm: thp: split huge page to any lower order pages. To: Zi Yan , "Matthew Wilcox (Oracle)" , Yang Shi , Yu Zhao , linux-mm@kvack.org Cc: "Kirill A . Shutemov" , Ryan Roberts , =?UTF-8?Q?Michal_Koutn=c3=bd?= , Roman Gushchin , Zach O'Keefe , Andrew Morton , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20230329011712.3242298-1-zi.yan@sent.com> <20230329011712.3242298-6-zi.yan@sent.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230329011712.3242298-6-zi.yan@sent.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A6B20180007 X-Rspam-User: X-Stat-Signature: 4niyg5bcpxgxyhqriwwx3oxroxd1utsh X-Rspamd-Server: rspam01 X-HE-Tag: 1691485285-269276 X-HE-Meta: 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 Tk0IuwCy bWJ8qgdz0laxkGcvtv5R6wrZkVsCqNpeiHhUYKs2V1CxvczImflqGm09t5FJ3GJKJ2gViYk6V6S2/4g52zqFL6WK/2CppIm95T8c3+Vszwpt47DYUFpGNctMXoJDQ9XYWt69NSxvSrpq1fpp7/LFFyXOVRsOWH3qaExHCmhCb50MTHLiktxobw2tcB6yodXCfg+tSqKpfD2TACwvE2H+sdD/SVlcK8nDFPi7V9BMFnzhahlh/NKgL8HPIyoynblyxfGkZGqOP7owTsxvSKnT0UpUr8KoYOTEkIh1EtmvhiDI5kk9TeuGsosKdRfG7jp11tmxVHJrAaIxiaqUxu4VDWVLnBxq7ozDNIqDIPzO5JsP8QLtcki5+qvgZF6W8Z+ZSRZEa53+k786OAwMVQ7ErOWTkcbWYxse3CZpIVfUP0m/p44dSXq8pgZWbag== 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 29.03.23 03:17, Zi Yan wrote: > From: Zi Yan > > To split a THP to any lower order pages, we need to reform THPs on > subpages at given order and add page refcount based on the new page > order. Also we need to reinitialize page_deferred_list after removing > the page from the split_queue, otherwise a subsequent split will see > list corruption when checking the page_deferred_list again. > > It has many uses, like minimizing the number of pages after > truncating a huge pagecache page. For anonymous THPs, we can only split > them to order-0 like before until we add support for any size anonymous > THPs. > Because I'm currently looking into something that would also not be compatible with order-1 for now: You should make it clear that order-1 is not supported, like: "mm: thp: split huge page to any lower order pages (except order 1)" And clarify in the subject why that is the case. -- Cheers, David / dhildenb