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[2003:d8:2f4e:3200:c99d:a38b:3f3a:d4b3]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-429897e785asm246899f8f.3.2025.10.22.13.22.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Oct 2025 13:22:11 -0700 (PDT) Message-ID: Date: Wed, 22 Oct 2025 22:22:08 +0200 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v12 mm-new 15/15] Documentation: mm: update the admin guide for mTHP collapse To: "Christoph Lameter (Ampere)" , Nico Pache Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, 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, 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, Bagas Sanjaya References: <20251022183717.70829-1-npache@redhat.com> <20251022183717.70829-16-npache@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 22.10.25 21:52, Christoph Lameter (Ampere) wrote: > On Wed, 22 Oct 2025, Nico Pache wrote: > >> Currently, madvise_collapse only supports collapsing to PMD-sized THPs + >> and does not attempt mTHP collapses. + > > madvise collapse is frequently used as far as I can tell from the THP > loads being tested. Could we support madvise collapse for mTHP? The big question is still how user space can communicate the desired order, and how we can not break existing users. So I guess there will definitely be some support to trigger collapse to mTHP in the future, the big question is through which interface. So it will happen after this series. Maybe through process_madvise() where we have an additional parameter, I think that was what people discussed in the past. -- Cheers David / dhildenb