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[95.233.25.82]) by smtp.gmail.com with ESMTPSA id x10-20020a5d490a000000b00317ab75748bsm16694129wrq.49.2023.08.09.06.00.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Aug 2023 06:00:33 -0700 (PDT) From: "Fabio M. De Francesco" To: Mike Rapoport Cc: Jonathan Corbet , Jonathan Cameron , Linus Walleij , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Ira Weiny , Matthew Wilcox , Randy Dunlap Subject: Re: [PATCH] Documentation/page_tables: Add info about MMU/TLB and Page Faults Date: Wed, 09 Aug 2023 15:00:31 +0200 Message-ID: <3770829.kQq0lBPeGt@suse> In-Reply-To: <20230807105010.GK2607694@kernel.org> References: <20230728120054.12306-1-fmdefrancesco@gmail.com> <20230807105010.GK2607694@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: B443AC0031 X-Stat-Signature: gagyhwx6e9k3yr4ohuo15bofprgydoeo X-HE-Tag: 1691586036-490611 X-HE-Meta: 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 I9qYfqGk yJG7/O+yE5W8+PT4YOh06/t7d5kXb4Ib/LYuK4sX76qk/IsWC9+OUmQCVYaUpafuz9poE+LrRPft6OvBBgTCPO2ahzFzkqS8aFcsk4JUQHFjSekiNVPCjCVQZbcVkNKUvepaYrkSOnvoVsfO2nnYglgV2Mz+0FgMRVqlEnyEx6VHNFabO8NoVPunR9k1ZBDQfoP2pv8RacFXvYopG+Mim5UGVmMPs1G0/P6jRfUtXCzhDAzwwseMB+PVWQfLOm5wNHo2stbS1ymjeXFZXrDZhv7wlJtbnNIMx01P+WoKBVNilsP1jGCB4kfLtdGHO18+n7n0zg1QHUrAd657hJVEE3DDVIZq3QCOdFBWKlSXuUgkJqnUngZrcR4IqE7kon1n95PntKuQ+7EeBQvhDnQe7onLehsjhakrTL8lvYIF97VkJ78ZQoiZwb6CGt8BzMwPBxC2f 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: On luned=EC 7 agosto 2023 12:50:10 CEST Mike Rapoport wrote: > Hi Fabio, >=20 > On Fri, Jul 28, 2023 at 01:53:01PM +0200, Fabio M. De Francesco wrote: > > Extend page_tables.rst by adding a section about the role of MMU and TLB > > in translating between virtual addresses and physical page frames. > > Furthermore explain the concept behind Page Faults and how the Linux > > kernel handles TLB misses. Finally briefly explain how and why to disab= le > > the page faults handler. > >=20 > > [snip] > > > > +MMU, TLB, and Page Faults > > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D > > + > > +The `Memory Management Unit (MMU)` is a hardware component that handles > > virtual +to physical address translations. It may use relatively small > > caches in hardware +called `Translation Lookaside Buffers (TLBs)` and=20 `Page > > Walk Caches` to speed up +these translations. > > + > > +When a process wants to access a memory location, the CPU provides a > > virtual > > +address to the MMU, which then uses the MMU to check access permission= s=20 and > > +dirty bits, and if possible it resolves the physical address and conse= nts > > the +requested type of access to the corresponding physical address. >=20 > Essentially any access to a memory location involves the translation from > virtual to physical, not only when processes access memory. Mike, I'm cutting everything from here on because I agree with your comments, so = I=20 could just write a long list of 'I agree', 'I understand' and the like. I w= ant=20 to avoid readers from the aforementioned list :-) I think (actually, I hope) that I have understood everything correctly. I w= ill=20 send a new version with the necessary corrections by the end of this week. Thanks again for your comments and suggestions. =46abio