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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6f0dea2179esm44146526d6.124.2025.04.11.17.44.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Apr 2025 17:44:06 -0700 (PDT) Date: Fri, 11 Apr 2025 20:44:04 -0400 From: Gregory Price To: Matthew Wilcox Cc: linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, donettom@linux.ibm.com, Huang Ying , Keith Busch , Feng Tang , Neha Gholkar Subject: Re: [RFC PATCH v4 0/6] Promotion of Unmapped Page Cache Folios. Message-ID: References: <20250411221111.493193-1-gourry@gourry.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam01 X-Stat-Signature: 4grtsszhyto8whax9676bsoe75umxzr6 X-Rspam-User: X-Rspamd-Queue-Id: D72B5100005 X-HE-Tag: 1744418647-636728 X-HE-Meta: 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 A7kKxULk UTX2mAuiH/uE6FBmUizaMehGcr8cmn/7PppKSHcH0Lw6gHeqB2QPyR+QR1exsNEIwGNzgdAefMbfYG0UaOxxbQoxV928Cx8fKxkcNQbstHIyJjDF+8YbywqRd9Mq9NKQCNDH91jye0tuWnxppOU/gLrzCOUkrAe8YpjDv1lirw+cHuoqTFEWQjUlU7ctJtvEurQDeuWX2xE9Cl138mo9D1OJyulv2+fnsvHue/lhRq0wSQR90CNL1/x3QiSfbEXPs5ro2nY6d4YCai3pCnkVm1tswqjE0n7gz7HP3TsD8q7QHZ9eqiOhV6F+sc3CvX8d0RihVMni0fd3xCnE= 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 Sat, Apr 12, 2025 at 01:35:56AM +0100, Matthew Wilcox wrote: > On Fri, Apr 11, 2025 at 08:09:55PM -0400, Gregory Price wrote: > > On Sat, Apr 12, 2025 at 12:49:18AM +0100, Matthew Wilcox wrote: > > > On Fri, Apr 11, 2025 at 06:11:05PM -0400, Gregory Price wrote: > > > > Unmapped page cache pages can be demoted to low-tier memory, but > > > > > > No. Page cache should never be demoted to low-tier memory. > > > NACK this patchset. > > > > This wasn't a statement of approval page cache being on lower tiers, > > it's a statement of fact. Enabling demotion causes this issue. > > Then that's the bug that needs to be fixed. Not adding 200+ lines > of code to recover from a situation that should never happen. Well, I have a use case that make valuable use of putting the page cache on a farther node rather than pushing it out to disk. But this discussion aside, I think we could simply make this a separate mode of demotion_enabled /* Only demote anonymous memory */ echo 2 > /sys/kernel/mm/numa/demotion_enabled Assuming we can recognize anon from just struct folio ~Gregory