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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4406203775bsm25557621cf.72.2024.06.11.08.20.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Jun 2024 08:20:09 -0700 (PDT) Date: Tue, 11 Jun 2024 11:20:01 -0400 From: Peter Xu To: Oscar Salvador Cc: Christophe Leroy , Andrew Morton , Jason Gunthorpe , Michael Ellerman , Nicholas Piggin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v5 02/18] mm: Define __pte_leaf_size() to also take a PMD entry Message-ID: References: <172b11c93e0de7a84937af2da9f80bd17c56b8c9.1717955558.git.christophe.leroy@csgroup.eu> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam03 X-Stat-Signature: a61qnechtoukb89itsnf99zr4srkozfd X-Rspamd-Queue-Id: 5435A20017 X-Rspam-User: X-HE-Tag: 1718119214-302604 X-HE-Meta: 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 +Oktf3Ws b+bKaUuGf1jY59vgX9QFsQ34PRl4Vt/lUlgdYmoqbxvnhDBKXZxT9z+I+Z9HNe5I/bEnfky19EozeLtnBt/p5J6EAqSDjBhwsLshUlQuqninBlaRbiXjJpVJRhCy6iKm2Wn4VqyAKV5U5s+8ttkEhZ0ymBeqOFl67XdY6UAAvxJmHVLkLhn4MnSXtGdh43ToKtR9CpBE87zlTA3u2pSAKzyx2gQFYXLq/cSF4N4hnBRXQ+JbcWhzte1/dB6MFVqlRmFCCcl1ZvSHwXpN/xoubYDxYOJkRtpxITSaMDFIoq1NGZAFR953NX7gactJ3ArxyOLDkluOzM2aBlsGKoKZeIO6cz/kMwf+RbhK8kaKpx1xauts= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000027, 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 Tue, Jun 11, 2024 at 05:08:45PM +0200, Oscar Salvador wrote: > The problem is that we do not have spare bits for 8xx to mark these ptes > as cont-ptes or mark them pte as 8MB, so I do not see a clear path on how > we could remove huge_ptep_get for 8xx. Right, I remember I thought about this too when I initially looked at one previous version of the series, I didn't come up yet with a good solution, but I guess we probably need to get rid of hugepd first anyway. We may somehow still need to identify this is a 8M large leaf, and I guess this is again the only special case where contpte can go over >1 pmds. > > I am really curious though how we handle that for THP? Or THP on 8xx > does not support that size? I'll leave this to Christophe, but IIUC thp is only PMD_ORDER sized, so shouldn't apply to the 8MB pages. Thanks, -- Peter Xu