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b=LX5O3pKpV5VL0ZUZNEqncE1v+B15dsGcei2/CP/ZTqDMCW4Ea0yScmeqikPgCjSj5 JSpn5GEIDCYssOh/aquUG5JpDIe/Sa1LK2h/LJc7CPl1GVjdnbQc0ReatV8tr4Wv+2 4uH85wTsnKZYTGQX7sBkFRqAFRhU8mxGW4B9hWkuQiCm81aCGyL5rYsA4VTBshSoG5 2WB+ZNvonbyQwPtvgW2czAohE/hit4kG6khYhYorU0LC49PKt4hLsiu5Rx7z0TGGUO MjUy6/9njSZ0Qv6ec5W+PdMgSjGA5pwrhuqRG4WniWcbld2s4JM1G/704cWfx5yKVH Z/dcXO8R7VWCA== Message-ID: <4ff89390-6f61-43d4-8cd0-6d56a1d448e9@kernel.org> Date: Mon, 1 Jun 2026 16:40:27 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v18 10/14] mm/khugepaged: introduce collapse_allowable_orders helper function To: Lorenzo Stoakes Cc: Nico Pache , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jack@suse.cz, jackmanb@google.com, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, liam@infradead.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com References: <20260522150009.121603-1-npache@redhat.com> <20260522150009.121603-11-npache@redhat.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: judmrjrk4h8h8u94mdg97qumen9z9sim X-Rspamd-Queue-Id: 188B5100014 X-Rspamd-Server: rspam07 X-Rspam-User: X-HE-Tag: 1780324840-225552 X-HE-Meta: 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 k+VB2D5V 2HUq9NJ9lML8jqGL9AEKhQxjWhkJBB1q5R4idsZXuvJmdtXhd2vSPsP3L4Fev1/zsbuc+7Bji87fOrV2HqxE0f1zEgNyMUJ4XKwz2j5OY8C6mUM3yedfhWH/gNQXlbuEu8AM181BWLNX2yxuY5PSL8/Cfe41QtiqCdQ7D57vSdtttJkNfhGixBpPTfTMQV9bAOEWRY6UB/CTC7VQpSr08bdI4awELmOntnK46nCaR6e4+PF3oh7cokCI8xDULY10w0k/whJTgpnb+gAhulrQflN+oaCG6xfhfVBTFopsDcrz9tFWBfiolRraEFwaX04iQ61WQsrG88Li/kuIbkAImP7up8vGkIS4UWBgGBDA0hLuk6B9JH+QMYdEq7A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/1/26 16:35, Lorenzo Stoakes wrote: > On Sun, May 31, 2026 at 10:18:16PM +0200, David Hildenbrand (Arm) wrote: >> On 5/22/26 17:00, Nico Pache wrote: >>> Add collapse_allowable_orders() to generalize THP order eligibility. The >>> function determines which THP orders are permitted based on collapse >>> context (khugepaged vs madv_collapse). >>> >>> This consolidates collapse configuration logic and provides a clean >>> interface for future mTHP collapse support where the orders may be >>> different. >> >> It would have been good to describe here that, for now, it only ever returns >> PMDs, and that it will be extended next. >> >> Logically, this patch belongs to #12, not #11 ... so seeing it before #11 was a bit >> >> ... and there, it is clear that we don't even want to know the orders? >> >> So can we just call this function >> >> "collapse_possible" and make it return a boolean? FWIW, I realized later that #11 has enabled_orders = collapse_allowable_orders(vma, vma->vm_flags, tva_flags); and forgot to delete that comment. So we must have a variant (for #11) that returns the enabled orders. > > Yeah agreed. > > But I also don't love the naming, we now have thp_vma_allowable_orders(), > __thp_vma_allowable_orders(), and then collapse_allowable_orders() and we also > have 3 different ways of collapsing, one of which we call MADV_... COLLAPSE, > and the other khugepaged + fault-in too for laughs. > > It's like a big circle of confusion. > > And of course we call THP collapse 'collapse' in general, so :) > > Anyway I'm fine with collapse_possible() so we can move on and then maybe > cleanup later. We could simply have collapse_possible_orders() and collapse_possible() the latter being a simple wrapper around collapse_possible_orders(). > > Also - if I look at khugepaged.c I see thp_vma_allowable_orders() still used in > hugepage_vma_revalidate(). > > Wouldn't it be better then to do the abstraction once mTHP order checking is > properly introduced and change this also and have _every_ order check be > consistent in khugepaged.c? That'd also be nice, if easily possible. -- Cheers, David