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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43d82dedc2dsm49307315e9.2.2025.03.27.14.06.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Mar 2025 14:06:31 -0700 (PDT) Date: Thu, 27 Mar 2025 21:06:25 +0000 From: David Laight To: guoren@kernel.org Cc: arnd@arndb.de, gregkh@linuxfoundation.org, torvalds@linux-foundation.org, paul.walmsley@sifive.com, palmer@dabbelt.com, anup@brainfault.org, atishp@atishpatra.org, oleg@redhat.com, kees@kernel.org, tglx@linutronix.de, will@kernel.org, mark.rutland@arm.com, brauner@kernel.org, akpm@linux-foundation.org, rostedt@goodmis.org, edumazet@google.com, unicorn_wang@outlook.com, inochiama@outlook.com, gaohan@iscas.ac.cn, shihua@iscas.ac.cn, jiawei@iscas.ac.cn, wuwei2016@iscas.ac.cn, drew@pdp7.com, prabhakar.mahadev-lad.rj@bp.renesas.com, ctsai390@andestech.com, wefu@redhat.com, kuba@kernel.org, pabeni@redhat.com, josef@toxicpanda.com, dsterba@suse.com, mingo@redhat.com, peterz@infradead.org, boqun.feng@gmail.com, xiao.w.wang@intel.com, qingfang.deng@siflower.com.cn, leobras@redhat.com, jszhang@kernel.org, conor.dooley@microchip.com, samuel.holland@sifive.com, yongxuan.wang@sifive.com, luxu.kernel@bytedance.com, david@redhat.com, ruanjinjie@huawei.com, cuiyunhui@bytedance.com, wangkefeng.wang@huawei.com, qiaozhe@iscas.ac.cn, ardb@kernel.org, ast@kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-mm@kvack.org, linux-crypto@vger.kernel.org, bpf@vger.kernel.org, linux-input@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-serial@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, maple-tree@lists.infradead.org, linux-trace-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-atm-general@lists.sourceforge.net, linux-btrfs@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, linux-nfs@vger.kernel.org, linux-sctp@vger.kernel.org, linux-usb@vger.kernel.org, linux-media@vger.kernel.org Subject: Re: [RFC PATCH V3 00/43] rv64ilp32_abi: Build CONFIG_64BIT kernel-self with ILP32 ABI Message-ID: <20250327210625.7a3021d0@pumpkin> In-Reply-To: <20250325121624.523258-1-guoren@kernel.org> References: <20250325121624.523258-1-guoren@kernel.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 25 Mar 2025 08:15:41 -0400 guoren@kernel.org wrote: > From: "Guo Ren (Alibaba DAMO Academy)" > > Since 2001, the CONFIG_64BIT kernel has been built with the LP64 ABI, > but this patchset allows the CONFIG_64BIT kernel to use an ILP32 ABI > for construction to reduce cache & memory footprint (Compared to > kernel-lp64-abi, kernel-rv64ilp32-abi decreased the used memory by > about 20%, as shown in "free -h" in the following demo.) ... Why on earth would you want to run a 64bit application on a 32bit kernel. IIRC the main justification for 64bit was to get a larger address space. Now you might want to compile a 32bit (ILP32) system that actually runs in 64bit mode (c/f x32) so that 64bit maths (long long) is more efficient - but that is a different issue. (I suspect you'd need to change the process switch code to save all 64bits of the registers - but maybe not much else??) David