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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-47183bc479fsm22813441cf.17.2025.02.10.07.47.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Feb 2025 07:47:59 -0800 (PST) Date: Mon, 10 Feb 2025 10:47:58 -0500 From: Gregory Price To: Byungchul Park Cc: "Harry (Hyeonggon) Yoo" <42.hyeyoo@gmail.com>, Honggyu Kim , kernel_team@skhynix.com, Matthew Wilcox , lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org Subject: Re: [LSF/MM/BPF TOPIC] Restricting or migrating unmovable kernel allocations from slow tier Message-ID: References: <20250207072024.GA48419@system.software.com> <20250210071741.GB39454@system.software.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250210071741.GB39454@system.software.com> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 38E7B40010 X-Stat-Signature: dctzjwdjha4kyy373ammufy8dpgkifzg X-HE-Tag: 1739202481-475733 X-HE-Meta: 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 yGQNtz/G Sq4rchkuxDVjyWeJ6nrUgak1e8Zcg5Uq5l1tp+rJyrH3uwasnnDu9rleENkv2XAhZ5AZPEJJvq4rnrovGeb1Ezwo4Q5ycKrSwPeVD6I/rmJSe3pc+NzXvdNT1XVM5YILZQVmVQtxDO3T01FmMBMozADFvckspkttldHdJKSSxfvF5NPgzGDuJik/YkulxwqauZclVA9MSH8WzKxlq7zRvY6ySn3QWzO4KLkbMImfzLNPsHxxaKtZX2I4xzVEuRssFRiW8FZfo+QSXn4kJkYGUYPZs+EKschBipDofYWxzznLUvp02b9yK5AF3i20w6tS2ptZJj94FwJXNC7qsBYrp14vrfcv4Cd+zdPdO3D1PUg9ugYjGmwh+TgKmyu/a8j59WmhO90RKIcXaEB4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.024920, 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 Mon, Feb 10, 2025 at 04:17:41PM +0900, Byungchul Park wrote: > On Mon, Feb 10, 2025 at 01:00:02AM -0500, Gregory Price wrote: > > > > You can probably actually (maybe?) collect data on this today - but > > you still have to contend with #2 and #3. > > Ah. You seem to mean those works should be serialized. Right? If it > should be for some reason, then it could be sensible. > I'm suggesting that there isn't a strong reason (yet) to consider such a complicated change. As Willy has said, it's a fairly fundamental change for a single-reason (CXL), which does not bode well for its acceptance. Honestly trying to save you some frustration. It would behoove you to find stronger reasons (w/ data) or consider different solutions. Right now there are stronger, simplers solutions to the ZONE_NORMAL capacity issue (struct page resize, huge pages) for possible capacities. I also think someone should actively ask whether `struct page` can be hosted on remote memory without performance loss. I may look into this. ~Gregory