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[96.255.20.138]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8849f9ae48fsm459499385a.24.2025.10.10.11.53.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Oct 2025 11:53:32 -0700 (PDT) Date: Fri, 10 Oct 2025 14:53:30 -0400 From: Gregory Price To: David Hildenbrand Cc: Michal Hocko , linux-mm@kvack.org, corbet@lwn.net, muchun.song@linux.dev, osalvador@suse.de, akpm@linux-foundation.org, hannes@cmpxchg.org, laoar.shao@gmail.com, brauner@kernel.org, mclapinski@google.com, joel.granados@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Mel Gorman , Alexandru Moise <00moses.alexander00@gmail.com>, Mike Kravetz , David Rientjes Subject: Re: [PATCH] Revert "mm, hugetlb: remove hugepages_treat_as_movable sysctl" Message-ID: References: <271f9af4-695c-4aa5-9249-2d21ad3db76e@redhat.com> <83e33641-8c42-4341-8e6e-5c75d00f93b9@redhat.com> <1d7476e6-5c6d-4175-b28d-3622222ea8e6@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1d7476e6-5c6d-4175-b28d-3622222ea8e6@redhat.com> On Fri, Oct 10, 2025 at 09:40:29AM +0200, David Hildenbrand wrote: > > > > Seems like this is pretty stable tbh. Obviously if you hack off the > > node0 hugepages migration fails - but I feel like you're signing up for > > that when you turn the bit on. > > Right, just needs to be documented thoroughly IMHO. > happy to make any doc adjustments. Better to move any notes every here though: https://lore.kernel.org/linux-mm/20251009161515.422292-1-gourry@gourry.net/T/#u --- Maybe worth finding some time at plumbers to discuss block-level allocation twiddly bits. Still not quite clear how this would pan out. Maybe it's as simple as adding GFP flags to blocks and having something like: echo NO_KERNEL > sys/bus/node/devices/node0/memory1234/eligibility echo PINNABLE > sys/bus/node/devices/node0/memory1234/eligibility folio_to_block(folio)->eligible(gfp) The issue here is obviously that it's clearly racey, in that a bit twiddle can change the eligibility mid-allocation. I'll think a bit more about this. ~Gregory