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Wong" , mcgrof@kernel.org, gost.dev@samsung.com, hch@lst.de, Pankaj Raghav References: <20250707142319.319642-1-kernel@pankajraghav.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: fne2UH7W5MgQlS6kgL1N3IxBYH_qe0RWXBOw_U92wpk_1752593225 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C2BED40005 X-Stat-Signature: 9t961wdzjy8jq1np3bjb79bxs8b7uu8p X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1752593228-665644 X-HE-Meta: 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 Rmj6Ulb3 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 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: List-Subscribe: List-Unsubscribe: On 15.07.25 17:25, Pankaj Raghav (Samsung) wrote: > On Tue, Jul 15, 2025 at 04:16:44PM +0200, David Hildenbrand wrote: >> On 15.07.25 16:12, Lorenzo Stoakes wrote: >>> On Tue, Jul 15, 2025 at 04:06:29PM +0200, David Hildenbrand wrote: >>>> I think at some point we discussed "when does the PMD-sized zeropage make >>>> *any* sense on these weird arch configs" (512MiB on arm64 64bit) >>>> >>>> No idea who wants to waste half a gig on that at runtime either. >>> >>> Yeah this is a problem we _really_ need to solve. But obviously somewhat out of >>> scope here. >>> >>>> >>>> But yeah, we should let the arch code opt in whether it wants it or not (in >>>> particular, maybe only on arm64 with CONFIG_PAGE_SIZE_4K) >>> >>> I don't think this should be an ARCH_HAS_xxx. >>> >>> Because that's saying 'this architecture has X', this isn't architecture >>> scope. >>> >>> I suppose PMDs may vary in terms of how huge they are regardless of page >>> table size actually. >>> >>> So maybe the best solution is a semantic one - just rename this to >>> ARCH_WANT_STATIC_PMD_ZERO_PAGE >>> >>> And then put the page size selector in the arch code. >>> >>> For example in arm64 we have: >>> >>> select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36) >>> >>> So doing something similar here like: >>> >>> select ARCH_WANT_STATIC_PMD_ZERO_PAGE if ARM64_4K_PAGES >>> >>> Would do thie job and sort everything out. >> >> Yes. > > Actually I had something similar in one of my earlier versions[1] where we > can opt in from arch specific Kconfig with *WANT* instead *HAS*. > > For starters, I will enable this only from x86. We can probably extend > this once we get the base patches up. Makes sense. -- Cheers, David / dhildenb