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Mon, 13 Apr 2026 07:15:29 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface MIME-Version: 1.0 X-ThreadId: Ax9AE_gslVNw Date: Mon, 13 Apr 2026 13:14:49 +0200 From: "Arnd Bergmann" To: "Mike Rapoport" , linux-sh@vger.kernel.org Cc: "Andrew Morton" , "John Paul Adrian Glaubitz" , "Rich Felker" , "Yoshinori Sato" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Message-Id: <42a4c6c1-762f-449f-9d14-3eb0fa02b94f@app.fastmail.com> In-Reply-To: <20260413104649.852228-1-rppt@kernel.org> References: <20260413104649.852228-1-rppt@kernel.org> Subject: Re: [PATCH 00/10] sh: remove NUMA and SPARSEMEM support Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5C77212000D X-Stat-Signature: m7fdnnk3bb6yer9kc3hxrhydu8ugumfm X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1776078931-653036 X-HE-Meta: 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 gORVEKMh X2LU80DUJFLWE/bHhOrM0nvUO5kJwoZ4uLYNTad2Q2v7iVstUqjp0A//TVvp26OxeYkH0/3BrTuY/tuUw9SqFT2JlNI55ohAHDw2pHG0MRXsIFnVstJs6umrDV0IaBFb6b8j13aJR9qoGmBIvJcvJB4394QR31c22ymUceno/QMRFqB9TLEt0aJ3WgpmILLu/FwvTZaeLoy0sn6X3oDEs9XtEtfEFXtzV0vY4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Apr 13, 2026, at 12:46, Mike Rapoport wrote: > > NUMA support for SuperH was introduced a long time ago by commit > b241cb0c885e ("sh: Support for multiple nodes.") > > "... for boards with many different memory blocks that are > otherwise unused (SH7722/SH7785 URAM and so forth)" > > In reality, this added 128K of memory on sh7722 and sh7785 and 256K on > shx3 at the expense of all the NUMA related code in the kernel. > > For build of v7.0-rc7 with defconfig and the same configuration with > CONFIG_NUMA disabled, bloat-o-meter reports difference of ~76k. Disabling > CONFIG_SPARSMEM on top increases the difference to ~94k. And that's only > overhead in code and static data that does not take into the account data > structures allocated at run time. > > And all this overhead has been there for nothing for almost 8 years > because since commit ac21fc2dcb40 ("sh: switch to NO_BOOTMEM") > those additional "nodes" could not be used by the core MM because the > maximal pfn for ZONE_NORMAL was cut out at the end of the normal memory. I had looked at it when you asked me about it last year, and I can confirm that agree with all your findings and the resulting patches. Whole series Reviewed-by: Arnd Bergmann Two very minor points: * It looks like you left the 'config SYS_SUPPORTS_NUMA' symbol in Kconfig, which no longer does anything, so this should probably be removed in patch 9 along with the lines that select it. * It appears that after your series, RISC-V is the only remaining architecture that supports NUMA in 32-bit mode, which I think we should not allow as a configuration, given that this would run into untested code and no hardware exists for it. Apparently commit 4f0e8eef772e ("riscv: Add numa support for riscv64 platform") intended this to only be for 64-bit targets but did not add a Kconfig dependency for CONFIG_64BIT (or CONFIG_SMP, which was added later). Arnd