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Shutemov" , John Hubbard , David Rientjes , Vlastimil Babka , Hugh Dickins , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v6 4/9] mm: thp: Introduce anon_orders and anon_always_mask sysfs files In-Reply-To: <20231009172029.e558c08dd90d9b94fec3a036@linux-foundation.org> References: <20230929114421.3761121-1-ryan.roberts@arm.com> <20230929114421.3761121-5-ryan.roberts@arm.com> <20230929155530.a51e68e03e47a06b6b84c689@linux-foundation.org> <87fs2mrqld.fsf@mail.lhotse> <20231009172029.e558c08dd90d9b94fec3a036@linux-foundation.org> Date: Thu, 12 Oct 2023 22:07:26 +1100 Message-ID: <87o7h4qett.fsf@mail.lhotse> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: C86A1140032 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 7o9frus8ncyoapnmujrwcgybwf66b53e X-HE-Tag: 1697108856-833926 X-HE-Meta: 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 5VTp+NbE tb1SvrkjfLkfwsWDwr02yaLgKuJYXBplOCYskmyu209F/xOsakgnhh61CKn30sqO+laH0Hz0Vz54wOqciFc4suDDHX0R3wOgKQPzmANqm92tsGoGuWCBI3biTNiJgIRlnUBeryI5lrqI2sKpwlULhppwI6omoVx1xt3ij8IFDbjUS+nizP2h1j8N14eFhH4Nz8v0eGVv5q1C/a/UIJhBQ3OTYV6vwOsHm8o8LVapc7wMJE36dQvLmCI33XhcdL3oJaedHkp81KjYj4Ms= 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: Andrew Morton writes: > On Sun, 08 Oct 2023 09:54:22 +1100 Michael Ellerman wrote: > >> > I don't know why powerpc's PTE_INDEX_SIZE is variable. >> >> To allow a single vmlinux to boot using either the Hashed Page Table >> MMU, or Radix Tree MMU, which have different page table geometry. >> >> That's a pretty crucial feature for distros, so that they can build a >> single kernel to boot on Power8/9/10. > > Dumb question: why can't distros ship two kernels and have the boot > loader (or something else) pick the appropriate one? I'm not a grub expert, but AFAIK it doesn't support loading a different kernel based on CPU/firwmare features. I'm quite sure it can't do that on powerpc at least. We also have another bootloader (petitboot) that is still supported by some distros, and can't do that. The other problem is like David says, distros are generally reluctant to add new kernel configurations unless they absolutely have to. It adds more work for them, more things to track, and can confuse users leading to spurious bug reports. cheers