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Mon, 22 Sep 2025 17:23:01 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: ksummit@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: AneuvEk2E7Kg Date: Mon, 22 Sep 2025 23:22:30 +0200 From: "Arnd Bergmann" To: "Nicolas Schichan" Cc: "Jason Gunthorpe" , "Geert Uytterhoeven" , ksummit@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, imx@lists.linux.dev, "Christophe Leroy" , "Richard Weinberger" , "Lucas Stach" , "Linus Walleij" , "Geert Uytterhoeven" , "Ankur Arora" , "David Hildenbrand" , "Mike Rapoport" , "Lorenzo Stoakes" , "Matthew Wilcox" , "Andrew Morton" , "Liam R. Howlett" , "Vlastimil Babka" , "Suren Baghdasaryan" , "Ira Weiny" , "Nishanth Menon" , =?UTF-8?Q?Heiko_St=C3=BCbner?= , "Alexander Sverdlin" , "Chester A. Unal" , "Sergio Paracuellos" , "Andreas Larsson" Message-Id: <598ab56d-7dd0-4adb-b0fe-30ad5cf24335@app.fastmail.com> In-Reply-To: References: <4ff89b72-03ff-4447-9d21-dd6a5fe1550f@app.fastmail.com> <20250917125951.GA1390993@nvidia.com> <02b0f383-1c43-4eeb-a76f-830c2970b833@app.fastmail.com> <547dcb81-434d-4910-aa7c-1d69019fcb3d@app.fastmail.com> <20250919143436.GC2132010@nvidia.com> <44f910bf-ac2c-4b2f-8e50-5cfc7dd0761a@app.fastmail.com> Subject: Re: [TECH TOPIC] Reaching consensus on CONFIG_HIGHMEM phaseout Content-Type: text/plain Content-Transfer-Encoding: 7bit On Mon, Sep 22, 2025, at 19:05, Nicolas Schichan wrote: >> On Fri, Sep 19, 2025, at 16:34, Jason Gunthorpe wrote: >> > On Fri, Sep 19, 2025 at 04:22:20PM +0200, Arnd Bergmann wrote: >> >> I did get an email from Nicolas Schichan (added to Cc here), >> and he is still supporting a widely deployed Kirkwood based >> platform that uses 1GB RAM configurations. He should get >> a chance to test that with CONFIG_VMSPLIT_3G_OPT, but I >> would expect that to continue working, possibly with minor >> bugfixes. > > We don't use HIGMEM on our Kirkwood platform, we are happy using a > 2G/2G WMSPLIT. We don't need a lot of virtual address space for > userland, and with the 2G split we don't waste physical memory. Ok, good. > I'm happy to test your patch serie with VMSPLIT_3G_OPT and see if it > still boots with it once you send it. The patches I did for turning off HIGHMEM on ARMv5 won't have any effect if you are already running without highmem, so I don't think we need to wait for your tests specifically. Any testing would be useful of course just to check that everything still works. Jason, I think we can go ahead with your suggestion. I can post my patches for review once I've done some testing on them. Arnd