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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id q131-20020a817589000000b00565eb8af1fesm1991442ywc.132.2023.06.27.13.13.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jun 2023 13:13:59 -0700 (PDT) Date: Tue, 27 Jun 2023 13:13:49 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: David Hildenbrand cc: Hugh Dickins , "Vishal Moola (Oracle)" , Andrew Morton , Matthew Wilcox , linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-openrisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, Catalin Marinas , Huacai Chen , Geert Uytterhoeven , Thomas Bogendoerfer , Dinh Nguyen , Jonas Bonn , Claudio Imbrenda , Paul Walmsley , "David S. Miller" , Richard Weinberger , Yoshinori Sato , Dave Hansen , Arnd Bergmann , Christophe Leroy Subject: Re: [PATCH v6 00/33] Split ptdesc from struct page In-Reply-To: Message-ID: <90e643ca-de72-2f4c-f4fe-35e06e1a9277@google.com> References: <20230627031431.29653-1-vishal.moola@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: E4EB040010 X-Rspam-User: X-Stat-Signature: ih6aek93p4oztrx9hak31b7oaa1qss6r X-Rspamd-Server: rspam01 X-HE-Tag: 1687896840-105797 X-HE-Meta: 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 ZKl4c/9o iEy/vohU5HRHro8bryD8VhTLjRthvIuNkS008BgGjs7+2hUcHdQAJe/uzXh4CQtj7gCNZyNiyewu/iC3az5mM2JJyfW6DDqzYynj3ky/r3/POsi669Kd/kSvvjPhyM2EkIGjcXAxErVIFDfjyEsGpdWtbPlq68mFotBWengvgysI9+ca5tUF5owOxZDFNMaw41sdzvAdFGk1riWMOs8Y24cIxtjYqdynkasdOQYHdjwfFi0mmeOIhgb0gxIF/tZXPKrNgezJyBvs91dE+TDdyYD/eLTgvhLTJACiCneXgX8bgQGuDazuw9TP9uN9mlFf9Bm3dW8hV/5EzDUah8WWxWhoI1T937rHmXm2wfJLCJegz/8EGjRpOY8MOSvXPgOR8rZV2jsp79JDdt3P9g7VYGrqQoZaFwcVtEy63COhd+PQNLm2LbGtkRkBppg== 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 Tue, 27 Jun 2023, David Hildenbrand wrote: > On 27.06.23 06:44, Hugh Dickins wrote: > > On Mon, 26 Jun 2023, Vishal Moola (Oracle) wrote: > > > >> The MM subsystem is trying to shrink struct page. This patchset > >> introduces a memory descriptor for page table tracking - struct ptdesc. > > ... > >> 39 files changed, 686 insertions(+), 455 deletions(-) > > > > I don't see the point of this patchset: to me it is just obfuscation of > > the present-day tight relationship between page table and struct page. > > > > Matthew already explained: > > > >> The intent is to get ptdescs to be dynamically allocated at some point > >> in the ~2-3 years out future when we have finished the folio project ... > > > > So in a kindly mood, I'd say that this patchset is ahead of its time. > > But I can certainly adapt to it, if everyone else sees some point to it. > > I share your thoughts, that code churn which will help eventually in the far, > far future (not wanting to sound too pessimistic, but it's not going to be > there tomorrow ;) ). > > However, if it's just the same as the other conversions we already did (e.g., > struct slab), then I guess there is no reason to stop now -- the obfuscation > already happened. > > ... or is there a difference regarding this conversion and the previous ones? I was aware of the struct slab thing, didn't see much point there myself either; but it was welcomed by Vlastimil, and barely affected outside of slab allocators, so I had no reason to object. You think that if a little unnecessary churn (a *lot* of churn if you include folios, which did save some repeated calls to compound_head()) has already occurred, that's a good precedent for allowing more and more? My opinion happens to differ on that. Hugh