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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 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-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, Nicholas Piggin , linux-mm@kvack.org, Christophe Leroy , Jason Gunthorpe , Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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