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[96.255.20.138]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4efd3437a5fsm110792271cf.27.2025.12.03.01.36.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Dec 2025 01:36:04 -0800 (PST) Date: Wed, 3 Dec 2025 04:36:02 -0500 From: Gregory Price To: "David Hildenbrand (Red Hat)" Cc: linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, osalvador@suse.de, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, muchun.song@linux.dev, Mel Gorman , Alexandru Moise <00moses.alexander00@gmail.com>, David Rientjes Subject: Re: [PATCH v3] mm, hugetlb: implement movable_gigantic_pages sysctl Message-ID: References: <20251203063836.187016-1-gourry@gourry.net> <305328e0-3011-409c-a040-76fc478d541a@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <305328e0-3011-409c-a040-76fc478d541a@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 4693A1C0010 X-Stat-Signature: pugk81kcdwamgd6r4wz7xfocofgzggiq X-HE-Tag: 1764754567-315860 X-HE-Meta: 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 5EOjIzhm bwKkb1etLQMKR58RWBNsi3i4g3ZvNgM4L5WabimYfRWakVvaVwC5Ihes1SpW9X29N11w8VpO6FS2IL8rNbCKNmNQ+lyi7BNmuTcLENiebwVaH6IfW5ntwM5ksp8m+wBNA9mcX+QMC6AHtAUTSO/a67ZwZq662zMZJgw99W8Ex31HjY5SKtXo6dwMfxRNmeKxJ3iGHu0i3JWShLj1p7ffXSM2DKZZq9VF866wwYtVO8tHqS2VIElKa/G4lZTcXMwZn1KEO02WKt4Izlbnj1at+S5k2mzvQm6wGNFLgARqsAQL0fCdwxzq5Ou3I2PxsrGYMOFx2urgnVRt/99UVXfdyUa3ZZWS5/YYMJpulFAv7uwWtRYU+C8ZGClbbUP527dQgVqHK8pEuUwrPHtEiv9Xou13Abc67vJjGEPblST9/QcNqeLuW9EJH05NKDPDpEDpYCLiVM9MteSxsRpCg8Olchsgapg== 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: On Wed, Dec 03, 2025 at 10:26:20AM +0100, David Hildenbrand (Red Hat) wrote: > On 12/3/25 07:38, Gregory Price wrote: > > This reintroduces a concept removed by: > > commit d6cb41cc44c6 ("mm, hugetlb: remove hugepages_treat_as_movable sysctl") > > > > This sysctl provides flexibility between ZONE_MOVABLE use cases: > > 1) onlining memory in ZONE_MOVABLE to maintain hotplug compatibility > > 2) onlining memory in ZONE_MOVABLE to make hugepage allocate reliable > > > > When ZONE_MOVABLE is used to make huge page allocation more reliable, > > disallowing gigantic pages memory in this region is pointless. If > > hotplug is not a requirement, we can loosen the restrictions to allow > > 1GB gigantic pages in ZONE_MOVABLE. > > > > Since 1GB can be difficult to migrate / has impacts on compaction / > > defragmentation, we don't enable this by default. Notably, 1GB pages > > can only be migrated if another 1GB page is available - so hot-unplug > > will fail if such a page cannot be found. > > In light of the other discussion: will it fail or will it simplt retry > forever, until there is a free 1g page? > ... > > +- When an admin sets the ``movable_gigantic_pages`` sysctl to true, gigantic > > + pages are allowed in ZONE_MOVABLE. This only allows migratable gigantic > > + pages to be allocated; however, if there are no eligible destination gigantic > > + pages at offline, the offlining operation will fail. > > Same question here. > Hah, great question. I will make a note to try this in the morning. > Nothing else jumped at me, in general as discussed, as long as it is opt-in > behavior > > Acked-by: David Hildenbrand (Red Hat) > > -- > Cheers > > David