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AJvYcCWuTB1QKbK7NuUFxczbtDHhTVOOCCiCr/xwHT8w01j3KqfHtcO0hKh4jUBIpS8BHdnbMaFFIIDNIay50jjj1YoxRVE= X-Gm-Message-State: AOJu0YwutuwI4VSjvJfxTaZMX3AH+w2llBuCqDay4MWc5rorkBxyJqQ4 3pqoF/yiZp64vk3utEK5EglTe3Flh5SM/XObBrMaO4uT/vwrd8Up X-Google-Smtp-Source: AGHT+IGJpazxnkj0vrfs0qcLRP6qpL8RKPrwMyfkdNMVp4bX1EZv/Ik/vGgVpgkEp8G6HmJcF19Ukw== X-Received: by 2002:a05:6870:8a12:b0:258:3455:4b02 with SMTP id 586e51a60fabf-26fe5ca588amr5544755fac.51.1723702678720; Wed, 14 Aug 2024 23:17:58 -0700 (PDT) Received: from [192.168.255.10] ([43.132.141.25]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7127add6b3dsm479443b3a.8.2024.08.14.23.17.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Aug 2024 23:17:58 -0700 (PDT) Message-ID: <02d7b8a2-b0d6-4713-b03e-5b22968387c3@gmail.com> Date: Thu, 15 Aug 2024 14:17:45 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 00/18] use struct ptdesc to replace pgtable_t To: Matthew Wilcox , alexs@kernel.org Cc: Will Deacon , "Aneesh Kumar K . V" , Nick Piggin , Peter Zijlstra , Russell King , Catalin Marinas , Brian Cain , WANG Xuerui , Geert Uytterhoeven , Jonas Bonn , Stefan Kristiansson , Stafford Horne , Michael Ellerman , Naveen N Rao , Paul Walmsley , Albert Ou , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Andy Lutomirski , Bibo Mao , Baolin Wang , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Qi Zheng , Vishal Moola , "Aneesh Kumar K . V" , Kemeng Shi , Lance Yang , Peter Xu , Barry Song , linux-s390@vger.kernel.org, Guo Ren , Christophe Leroy , Palmer Dabbelt , Mike Rapoport , Oscar Salvador , Alexandre Ghiti , Jisheng Zhang , Samuel Holland , Anup Patel , Josh Poimboeuf , Breno Leitao , Alexander Gordeev , Gerald Schaefer , Hugh Dickins , David Hildenbrand , Ryan Roberts References: <20240730064712.3714387-1-alexs@kernel.org> Content-Language: en-US From: Alex Shi In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: i6jreu4nsshj73a1hbd7x4fwnfqpdusn X-Rspamd-Queue-Id: C579940003 X-Rspamd-Server: rspam11 X-HE-Tag: 1723702679-858373 X-HE-Meta: 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 k5XNEjya 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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 8/15/24 1:13 AM, Matthew Wilcox wrote: > On Tue, Jul 30, 2024 at 02:46:54PM +0800, alexs@kernel.org wrote: >> We have struct ptdesc for page table descriptor a year ago, but it >> has no much usages in kernel, while pgtable_t is used widely. > > Hum, I thought I responded to this to point out the problem, but > I don't see the response anywhere, so I'll try again. > >> The pgtable_t is typedefed as 'pte_t *' in sparc, s390, powerpc and m68k >> except SUN3, others archs are all same as 'struct page *'. > > And there's a very good reason for that. On s390 and powerpc (I cannot > speak to the sparc/m68k), each page table is (potentially) smaller > than PAGE_SIZE. So we cannot do what your patch purports to do, as > we would not know whether we're referring to the first or subsequent > page tables contained within a page. >> Maybe at some point in the distant future we'll be able to allocate > a ptdesc per page table instead of per page allocated for use by page > tables. But we cannot do that yet. Got it. Thanks a lot for the info!