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b=PZJPbnJmAfhpO7Ga0JnK6KzeGeWKWKjs35aPU8TqVKym3tDfbrHObrcmottgr/1Wk fgH5RfYipAgTJnqYgcT3H7iBBMICLhLQx4W3sN4nbZvP/jirAi+1BwgbaFgi9PfMii 7a7YamJDkaOiDNuvPvL0LNVzoMfMBcEfrYJbIlDirg2lA82tWCJ9RxeCYrF78Qegd5 oCMV5PgNctEx5UfyRRSkRpt7i5LeC1dmNk/XoXRMVNzHRouZ687pmToxH/bY/OndNq wK268y6wXIGUTxLU1UuFcb+wHS2NnSnPzo+DrwjTqUGfoHv03fVfQwxhPnIpV9Flya kmYLoKqglyu6g== Message-ID: <989e3584-4008-4c5b-a49f-ed84b656ed14@kernel.org> Date: Fri, 18 Sep 2026 15:57:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/4] mm: allow shared folios to be promoted to a fast tier To: Gregory Price Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, jannh@google.com, pfalcato@suse.de, osalvador@suse.de, hannes@cmpxchg.org, raghavendra.kt@amd.com, stable@vger.kernel.org References: <20260911001826.2109390-1-gourry@gourry.net> <20260911001826.2109390-3-gourry@gourry.net> <41b46756-ed02-439c-ab72-e32a84fc7f17@kernel.org> 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: 3q7i7djnogq5tp3qa83zoit7ip4o1j9w X-Rspam-User: X-Rspamd-Queue-Id: 5E5AF140007 X-Rspamd-Server: rspam03 X-HE-Tag: 1789739891-250277 X-HE-Meta: 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 QSi/pwFa NXUq2A+/b/TKF7VT0CQx2YwR1T0IphrsH/DtBx9ZWOeKVHUf+6uofAe9lDCuPzlWWZwN77rNpqzePAzOA7kE17CIrXXSC2+eDmNPdzDCPf2CEg8Z9g0tg9m0/pa2+wMy4+HG9hNWSM8w3HVBdCpTwW5bjKT3MG6pXA9ugTvqUXvXKMHOf78ZwhA39DwQQcEv/kcsytwdvyTHwNsaGfUcLfohsq0plqGpCptcymz2gmZ7pwhO+rydruF3ZmIBE+dt5CamHIM6/pMUyMNQWqGLnC9NgFyrpVkqtYHyPy/8xY4NEDsfuyTsf5Zed0HEKSL505XDp+Xm9/SsuLW/Kdl0uikfKFUW3CuGT8Ovicex8E7yUMP7NWX02Zsx6URCK2yxhctAnmT20bGniNzQcdibNC59U2TNeRdwPR42yo85ti/kddcA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/18/26 15:54, Gregory Price wrote: > On Fri, Sep 18, 2026 at 02:53:40PM +0200, David Hildenbrand (Arm) wrote: >> On 9/11/26 02:18, Gregory Price wrote: >>> From: "Gregory Price (Meta)" >>> >>> NUMA balancing rejects shared copy-on-write folios and executable >>> file folios mapped by multiple processes to avoid placement bouncing. >>> These checks also block promotion from slow memory. >> >> Right. How to we know the direction of promotion vs. demotion, though? >> > > numa balancing never demotes. It either: > > 1) moves between sockets (nodes w/ N_CPU) (NORMAL) > or > 2) moves from !top_tier to top_tier (TIERING) > > Demotion is only enacted in reclaim / vmscan, and has no coupling with > numa balancing. > Valuable to briefly mention that here, and have some helper functions that make this obvious (and maybe document it as well ;) ) :) -- Cheers, David