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AJvYcCXKej78JXPPJ47sDv+VeAAFxfhgvMsj+0Zpmpx8vZtwBTrk2EaQsAIFVuOi2qa+/fZ0VFNoNGA6wA==@kvack.org X-Gm-Message-State: AOJu0YyRDitkWsu8dADzBOnlZZtDbZijytX+KLGHmjgQleqbeXHDhLhJ 6ux75ArjVhPUFiTTxkGRUmsMYkdXUSNLB2JiszwXICdrjmC8iRXMXf32IPa+00ACPftf3kjI9ir fM+Oa4zdVFULV7A== X-Received: from wmpl26.prod.google.com ([2002:a05:600c:89a:b0:47e:ddf0:fd00]) (user=jackmanb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:4e16:b0:483:6d4a:7e6d with SMTP id 5b1f17b1804b1-4855670cd92mr222236695e9.30.1773676889811; Mon, 16 Mar 2026 09:01:29 -0700 (PDT) Date: Mon, 16 Mar 2026 16:01:28 +0000 In-Reply-To: <5d22bf8810fc18c326e1b12c90994a72f74916a7.camel@intel.com> Mime-Version: 1.0 References: <20260225-page_alloc-unmapped-v1-0-e8808a03cd66@google.com> <5d22bf8810fc18c326e1b12c90994a72f74916a7.camel@intel.com> X-Mailer: aerc 0.21.0 Message-ID: Subject: Re: [PATCH RFC 00/19] mm: Add __GFP_UNMAPPED From: Brendan Jackman To: "Edgecombe, Rick P" , "jackmanb@google.com" , "dave.hansen@linux.intel.com" , "bp@alien8.de" , "david@kernel.org" , "peterz@infradead.org" , "lorenzo.stoakes@oracle.com" , "hannes@cmpxchg.org" , "weixugc@google.com" , "vbabka@kernel.org" , "akpm@linux-foundation.org" , "ziy@nvidia.com" Cc: "kalyazin@amazon.co.uk" , "rppt@kernel.org" , "luto@kernel.org" , "yosry.ahmed@linux.dev" , "linux-kernel@vger.kernel.org" , "reijiw@google.com" , "linux-mm@kvack.org" , "itazur@amazon.co.uk" , "patrick.roy@linux.dev" , "sumit.garg@oss.qualcomm.com" , "tglx@kernel.org" , "will@kernel.org" , "rientjes@google.com" , "derkling@google.com" , "david.kaplan@amd.com" , "x86@kernel.org" Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: B867BC000E X-Rspamd-Server: rspam08 X-Stat-Signature: 8oe1nr1s51i8x1qt7hf8zjkn4s99guhz X-HE-Tag: 1773676891-401342 X-HE-Meta: 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 Gn/nZbJS 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Rick, sorry I was just scanning over this thread again while prepping the next version and noticed I never replied to this. On Fri Mar 6, 2026 at 5:38 PM UTC, Rick P Edgecombe wrote: > On Wed, 2026-02-25 at 16:34 +0000, Brendan Jackman wrote: >> __GFP_UNMAPPED > > Haven't looked at this in detail, but there was some previous work that even > used the same flag name. In the end, the discussion leaned towards a dedicated > API instead of a flag. Not saying the flag approach is dead, but might useful to > explain how it fits in with that discussion. > > https://lore.kernel.org/lkml/20230308094106.227365-1-rppt@kernel.org/ I am not at all wed to using a GFP flag for this, but a key difference between this and Mike's original __GFP_UNMAPPED is that this is integrated directly into the page allocator itself, and that's a load bearing element. Technically speaking, in this series __GFP_UNMAPPED is only supported for unmovable allocations, but that's just to avoid bloating the data structures (there isn't a user for that type of allocation yet, so there's no point in creating freelists for it). But, in principle, the goal here is to support all the fancy stuff that the mm does for this memory. That's important because for the real usecases I have in mind here, the vast majority of memory in the system should eventually be relying on the page allocator to unmap it (either completely as in __GFP_UNMAPPED, or just from the special ASI pagetables as in __GFP_SENSITIVE, which will be added later). So, yeah we can always have a special API but that would be a bit of a roundabout way to just save a bit in a an enum, it wouldn't actually represent any simplification of the page allocator's API. Anyway thanks for pointing this out, I will neded to explain this in the next version's cover letter, but in the meantime there's a quick braindump of my thinking.