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[2003:d8:2f3f:4b00:ee13:8c22:5cc5:d169]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4772899fdf0sm87665605e9.3.2025.10.31.04.12.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 31 Oct 2025 04:12:40 -0700 (PDT) Message-ID: <1c0c89d3-0f72-4631-b1fc-41e1426c8bed@redhat.com> Date: Fri, 31 Oct 2025 12:12:37 +0100 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v12 mm-new 06/15] khugepaged: introduce collapse_max_ptes_none helper function To: Lorenzo Stoakes Cc: Nico Pache , 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, 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: <20251022183717.70829-1-npache@redhat.com> <20251022183717.70829-7-npache@redhat.com> <5f8c69c1-d07b-4957-b671-b37fccf729f1@lucifer.local> <74583699-bd9e-496c-904c-ce6a8e1b42d9@redhat.com> <3dc6b17f-a3e0-4b2c-9348-c75257b0e7f6@lucifer.local> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit >>>> "eagerness" would not be like swappiness, and we will really have to be >>>> careful here. I don't know yet when I will have time to look into that. >>> >>> I guess I missed this part of the converastion, what do you mean? >> >> Johannes raised issues with that on the list and afterwards we had an >> offline discussion about some of the details and why something unpredictable >> is not good. > > Could we get these details on-list so we can discuss them? This doesn't have to > be urgent, but I would like to have a say in this or at least be part of the > converastion please. Sorry, I only found now time to reply on this point. Johannes raised the point in [1], and afterwards we went a bit into detail in a off-list discussion. In essence, I think he is right that is something we have to be very careful about. So it turned out as something that will take a lot more time+effort on my side than I originally thought, turning it not feasible in the short term given how I already lack behind on so many other things. So I concluded that it's probably best to have such and effort be independent of this series. And in some way it is either way, because max_ptes_none is just a horrible interface given the values are architecture dependent. I'll be happy if we can focus in this series on the bare minimum initial support, and avoid any magic (scaling / capping) as it all turned out to be much more tricky (interaction with the deferred shrinker ...) than most of us initially thought. But I think we're already on the same page here, just wanted to share a bit more details on the max_ptes_none vs. eagerness idea. [1] https://lkml.kernel.org/r/20250915134359.GA827803@cmpxchg.org -- Cheers David / dhildenb