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[2003:d8:2f18:f900:e0ae:65d5:8bf8:8cfd]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45e037c4490sm172678095e9.19.2025.09.15.03.25.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 15 Sep 2025 03:25:59 -0700 (PDT) Message-ID: <78d75263-e0ab-4dcd-ae97-5c5c9bb10193@redhat.com> Date: Mon, 15 Sep 2025 12:25:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 00/15] khugepaged: mTHP support To: Lorenzo Stoakes Cc: Kiryl Shutsemau , Nico Pache , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.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, 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: <20250912032810.197475-1-npache@redhat.com> <43f42d9d-f814-4b54-91a6-3073f7c7cedf@redhat.com> <80c50bf4-27b1-483c-9977-2519369c2630@redhat.com> <7ri4u7uxsv6elyohqiq2w5oxv4yhk2tyniwglfxtiueiyofb3n@l4exlmlf5ty4> <59641180-a0d9-400c-aaeb-0c9e93954bf5@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: DE9251A000C X-Stat-Signature: uiaw6ooprnkoby7bbur3u1e9p8nfou6i X-Rspam-User: X-HE-Tag: 1757931964-760197 X-HE-Meta: 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 MT2Y5JAa 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 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: >> >> I would just say "The kernel might decide to use a more conservative approach >> when collapsing smaller THPs" etc. >> >> >> Thoughts? > > Well I've sort of reviewed oppositely there :) well at least that it needs to be > a hell of a lot clearer (I find that comment really compressed and I just don't > really understand it). Right. I think these are just details we should hide from the user. And in particular, not over-document it so we can more easily change semantics later. > > I guess I didn't think about people reading that and relying on it, so maybe we > could alternatively make that succinct. > > But I think it'd be better to say something like "mTHP collapse cannot currently > correctly function with half or more of the PTE entries empty, so we cap at just > below this level" in this case. IMHO we should just say that the value might be reduced for internal purposes and that this behavior might change in the future would likely be good enough. -- Cheers David / dhildenb