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Shutemov" To: Peter Zijlstra Subject: Re: [PATCH 1/4] treewide: remove unused address argument from pte_alloc functions (v2) Message-ID: <20181025104703.esl6wxyg2ihe4zoc@kshutemo-mobl1> References: <20181013013200.206928-1-joel@joelfernandes.org> <20181013013200.206928-2-joel@joelfernandes.org> <20181024083716.GN3109@worktop.c.hoisthospitality.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181024083716.GN3109@worktop.c.hoisthospitality.com> User-Agent: NeoMutt/20180716 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-mips@linux-mips.org, Rich Felker , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Catalin Marinas , Dave Hansen , Will Deacon , Michal Hocko , linux-mm@kvack.org, lokeshgidra@google.com, "Joel Fernandes \(Google\)" , linux-riscv@lists.infradead.org, elfring@users.sourceforge.net, Jonas Bonn , kvmarm@lists.cs.columbia.edu, dancol@google.com, Yoshinori Sato , sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-hexagon@vger.kernel.org, Helge Deller , "maintainer:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)" , hughd@google.com, "James E.J. Bottomley" , kasan-dev@googlegroups.com, anton.ivanov@kot-begemot.co.uk, Ingo Molnar , Geert Uytterhoeven , Andrey Ryabinin , linux-snps-arc@lists.infradead.org, kernel-team@android.com, Sam Creasey , Fenghua Yu , linux-s390@vger.kernel.org, Jeff Dike , linux-um@lists.infradead.org, Stefan Kristiansson , Julia Lawall , linux-m68k@lists.linux-m68k.org, Borislav Petkov , Andy Lutomirski , nios2-dev@lists.rocketboards.org, Stafford Horne , Guan Xuetao , Chris Zankel , Tony Luck , Richard Weinberger , linux-parisc@vger.kernel.org, Max Filippov , pantin@google.com, linux-kernel@vger.kernel.org, minchan@kernel.org, Thomas Gleixner , linux-alpha@vger.kernel.org, Ley Foon Tan , akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, "David S. Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Oct 24, 2018 at 10:37:16AM +0200, Peter Zijlstra wrote: > On Fri, Oct 12, 2018 at 06:31:57PM -0700, Joel Fernandes (Google) wrote: > > This series speeds up mremap(2) syscall by copying page tables at the > > PMD level even for non-THP systems. There is concern that the extra > > 'address' argument that mremap passes to pte_alloc may do something > > subtle architecture related in the future that may make the scheme not > > work. Also we find that there is no point in passing the 'address' to > > pte_alloc since its unused. So this patch therefore removes this > > argument tree-wide resulting in a nice negative diff as well. Also > > ensuring along the way that the enabled architectures do not do anything > > funky with 'address' argument that goes unnoticed by the optimization. > > Did you happen to look at the history of where that address argument > came from? -- just being curious here. ISTR something vague about > architectures having different paging structure for different memory > ranges. I see some archicetures (i.e. sparc and, I believe power) used the address for coloring. It's not needed anymore. Page allocator and SL?B are good enough now. See 3c936465249f ("[SPARC64]: Kill pgtable quicklists and use SLAB.") -- Kirill A. Shutemov