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b=uqXZJF63sweS9rbp4xNKKiVg6CPHseMPnaKDYO7JRf+hWWLkRcZLC3YNj692EulQy JCMsfOkFmyb3VbWv/eztxY30WQKamopYAS9ENw41MX6rhf79onZJeqhESKv8qhDrYT K3ongKIWUSpOS0fbSOAiFXgCDIxb0Ct0NRw8s4iBDAC9zLCQmCubgR8FDEA1Wki5B9 6VKIx2xQsRsEOFFEcEXTxp1iwYm1yWP1OQZUF8pNU9rgTq7m+df0TZ/pywau9QWp9g LWvLJQxkqT/wy1VwyV1CcxhAHZQRoymaD09kZfIruhwYSgIq6rfpMW5qpRdmP0dcIZ B6IXqXneBfmew== Message-ID: Date: Thu, 8 Jan 2026 17:09:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 mm-new 00/16] khugepaged: mTHP support To: Nico Pache , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, akpm@linux-foundation.org, baohua@kernel.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kas@kernel.org, aarcange@redhat.com, raquini@redhat.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org, hughd@google.com, richard.weiyang@gmail.com, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, jannh@google.com, pfalcato@suse.de References: <20251201174627.23295-1-npache@redhat.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: txfzn4qb3zk5wxbjuygoiyr3iydihg3m X-Rspamd-Queue-Id: 726C51A001A X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1767888603-909392 X-HE-Meta: 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 rpwIfJ2L /jjYuEml4W2qU6MQfTntNaHRQXPZjHd+iS59a0eUfX71nyGDdjnyttD9b2Q1S+c7h/wKcpk9ceu4261N64u9XwhW78cmGg5xDyq/GSfSKSOLx9PZTNle8S7vGB0pgCu6mw0wphEoNiSDJ+mBN66OuIyX/Xa8oIYC64jNHTcHggclwn/Bzj8rm7os16BP918exE507jniV+dd+rRK0ks6sgmbFGeXOtah/IPyKPFbHYUNFDCcEotUzEvNuWc436xBDVUfzFnL1xy8IXS0LLpNDGNUJNXWEQqe/p5ZYW51dmAUx4vqUIEWlEImg69WPl3xhEu7SpUYpARS4nCw= 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: List-Subscribe: List-Unsubscribe: On 12/1/25 18:46, Nico Pache wrote: > The following series provides khugepaged with the capability to collapse > anonymous memory regions to mTHPs. > > To achieve this we generalize the khugepaged functions to no longer depend > on PMD_ORDER. Then during the PMD scan, we use a bitmap to track individual > pages that are occupied (!none/zero). After the PMD scan is done, we use > the bitmap to find the optimal mTHP sizes for the PMD range. The > restriction on max_ptes_none is removed during the scan, to make sure we > account for the whole PMD range in the bitmap. When no mTHP size is > enabled, the legacy behavior of khugepaged is maintained. > > We currently only support max_ptes_none values of 0 or HPAGE_PMD_NR - 1 > (ie 511). If any other value is specified, the kernel will emit a warning > and no mTHP collapse will be attempted. If a mTHP collapse is attempted, > but contains swapped out, or shared pages, we don't perform the collapse. > It is now also possible to collapse to mTHPs without requiring the PMD THP > size to be enabled. These limitiations are to prevent collapse "creep" > behavior. This prevents constantly promoting mTHPs to the next available > size, which would occur because a collapse introduces more non-zero pages > that would satisfy the promotion condition on subsequent scans. > > Patch 1: Refactor/rename hpage_collapse > Patch 2: Refactoring to combine madvise_collapse and khugepaged These two patches could get queued already separately, right? -- Cheers David