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b=kkXNWJ7/M92XbIIqnCuSwyLr03O6/AkVzdoi51qjOyTquwaczjPVNNy12MGWk6Spy u0ZCafMK5PDn2oPazYAk/LGZJybB3Bd/1QlSHWEnjdpDvRpFnj+Dlx6imHk6kmRj2W GmtdGnpMa40At7JPZUfzH5PbQeT8wxc5sijxivhr9ls2A3CGyX862g2P9luWNVByyz +vcqvRyI/R7zUU4xbykN0lMFXJwa/DBYQWMkhRzJ1Zz0ap1BJpPahRn8CylVj6ZKkJ oN1OFD/eEvVZqaAJtm/5BUCTOuAsmVApZyoJO+2mkrEd0UcXOPjvWARBVm4r3r7+li pSJVprhHvq2jw== Date: Tue, 28 Apr 2026 18:34:30 +0200 From: Mike Rapoport To: Arnd Bergmann Cc: linux-sh@vger.kernel.org, Andrew Morton , John Paul Adrian Glaubitz , Rich Felker , Yoshinori Sato , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 00/10] sh: remove NUMA and SPARSEMEM support Message-ID: References: <20260413104649.852228-1-rppt@kernel.org> <42a4c6c1-762f-449f-9d14-3eb0fa02b94f@app.fastmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <42a4c6c1-762f-449f-9d14-3eb0fa02b94f@app.fastmail.com> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 4C7B9140004 X-Rspam-User: X-Stat-Signature: 37r4qt96714f8xg7ow7eq7uf3d9wfhji X-HE-Tag: 1777394079-306688 X-HE-Meta: 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 +jQMk7Sr w5HLQa+rqUfszGVnCNML8zVH1HnqdTy0pmFFId3ZtqX7azQdM82yWzlsrdbmK8aTMSj9mpV603gCCHSui2uWQ4RBHgITOW0hXkxH/yvoqRU8afn0EpHu5+ENmEM6OFCf62fvhOfVlsJNeTX7xKvTCNaQBxej573h+dYMmYVIZtyEByhoSzQnkzNjDNvOe/JoXN95x5SJneM8GfJnH1gIrJJJBu8vVDZoNmCEr2NtPg1q45UZvSuB8mFdiTTASDoD0ZB8R Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: (oops, missed that earlier) On Mon, Apr 13, 2026 at 01:14:49PM +0200, Arnd Bergmann wrote: > 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 Thanks! > 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. I think it better fits patch 1 that removes CONFIG_NUMA, patch 9 is about SPARSEMEM. > * 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). I can send a patch to RISC-V for it. > Arnd -- Sincerely yours, Mike.