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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-92e90bb91adsm1705974285a.20.2026.07.09.10.32.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jul 2026 10:32:22 -0700 (PDT) Date: Thu, 9 Jul 2026 13:32:18 -0400 From: Gregory Price To: "Huang, Ying" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, kernel-team@meta.com, willy@infradead.org, jack@suse.cz, akpm@linux-foundation.org, david@kernel.org, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, apopple@nvidia.com, Johannes Weiner Subject: Re: [PATCH 0/2] mm: don't apply task mempolicy to unmovable kernel allocations Message-ID: References: <20260701222112.2820098-1-gourry@gourry.net> <87echco1w6.fsf@DESKTOP-5N7EMDA> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87echco1w6.fsf@DESKTOP-5N7EMDA> X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 8808A80007 X-Stat-Signature: ktkphbasztgm3h6adgupkqp73bsbzksg X-HE-Tag: 1783618343-371980 X-HE-Meta: U2FsdGVkX19+5RaCNXS+AcY4lIX0iZJGCTN9KJ332APS+GzAoC3z07EiHky4G7F1FxTknX/13YLqs8MYrgdx/Y6LhqPuMbYNWOy+anhjyJJR6qFYWU8enPUCymTCJu6hj4CYgo1ZHW/SxSsZZDVQDyMoaOr012ntEYpqSNdhoEBa/8BfBuHj0M/kjnx9T6IyjPRkRnqGvl6b4SLlL6ke4gDDiPExaHh3MbCFxQHkN3LPcmcrrWzVPiq4gSp4mGgrM9C3oDwP651JAlwB8GeQqAiqUpppgNGPpuoh9VE/1mTT4Ts7Jj5GWqkzASgX//35A/NnZdHkgkIItPYI4zjNn0rVIUwyzm0VUYgn95EX3zkM+O9GcbPy82cCv68GdpO7qEspIoh59yFfyQwTPtWvTyTNs5/CQgmXgmjScBvPiPksHP/8IEdPC5oXr+i2UfXOqR/FqU6o8Q2QLBNQtRkDt2xamniiFKDu7oztyes96f1zJC2dv4x8I2FU/6NL4ANRPoUsLJQMls8obTKHt02eXDXd48f5nO1gjSY6cPoo+7849TFkRdoFmcXK40G9JnruKzQyDmMD0ZeOewB8E5H3b3Vh0C4Nfw8zfWkrUkKru6VdzTlDbQ2Lcf5tY/bM4O9cmt8+Pb951dgGVh/HL7JJg8IcN4JTUyA6o3awKg6Z02x4llAYtmWZ8c3rdMCqzX7rYY7p3FoNTGl2m3dJ9ISrE/3kA54iY9bj5qL2Fere3JEnNuOE91J020aEtWeLTbh350YvTDKSMMHYmGbNiBjpJdekCBglQCv9OpYfUJf6ni0U+7deKbJfmhS6f1YfOiw7AtPPjjwPJTN83BHqaNxU++sJvJupoEdxU2z4Ug3GZX8P6+69nWQgzzT6pA6rxlL+hlFv2lE3QMxn6mHqR7/GerrPmsI8k8OW4h7AaI1CdgBkNcygHp4K1yZaJtK+WUll6g8MQCi5AGyqqQI/1lN nclltJBP 02NomAguc6rKHTCow8el9Thu7DX8ASwMXidkojnjItdQhltAm+IOj22Pm3nScpNu2JdcxH4Q9+mUVPQORdVxuH4GQqDj+wVL4CjfhrvUFIV5nSspOjh9zLiLu/fJ4Ub4dDibbJlXql8P17mqRU/gZ5Im96thLn26dFupyQlJ+papyKcN0Nrn7UDFfQ/+n1xQ6IAqQarWVZEguICg9+9i61XCHSfEskg7WqVX543mI1Vz6sFM41GjLZhgGi76vpXRQWCef+L/CYQuf6HRMOM7WyLw4IEvzaEl8LqKqY2vaNKSm6SEfDdKpr5M7unFleGfPMzk6uuDVDfoz2CzMIqunBFury+sELgGmfURTT6yGmdc07fb/kvQ6owjcFlwNHKiqQx2jBMEVxiwS6NPicciDWpsqY4cuy6rgku4Z7c4OClNMhlvwDVcu9N9a7/y48fSWa+9AdnQePs++aGVX9Vt5KYv7Vg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jul 09, 2026 at 07:09:29PM +0800, Huang, Ying wrote: > Gregory Price writes: > > > The unmovable unaccounted kernel allocations stop following the > > task policy and place node-local. With no policy set, both place > > node-local as before. > > Personally, I think this should be the right thing to do theoretically. > However, you may need to find some practical issues that this resolves. > I don't entirely disagree, but there is at least one scenario where this is an obvious improvement: BIOS-configured CXL memory brought up in ZONE_NORMAL. An task interleave policy on such a system will end up with unaccounted kernel allocations landing on the remote node, which is just not preferable at all (and uncorrectable). It's not a complete fix (fallbacks can still occur under pressure), but it's one piece of the puzzle. Forward looking: This patch makes private-node's with ZONE_NORMAL reliably hot-un-pluggable. But that improvement is obviously predicated on work that isn't upstream (yet :] ). I need to send a v2 of this with SLAB_ACCOUNT fixed up, and some numbers to justify dropping the pagecache fix. But I will probably sandbag this a bit until i finally send out v5 of private nodes. ~Gregory