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Sat, 08 Mar 2025 16:08:27 -0800 (PST) Date: Sat, 8 Mar 2025 16:08:24 -0800 From: Charlie Jenkins To: Thomas Gleixner Cc: Paul Walmsley , Palmer Dabbelt , Huacai Chen , WANG Xuerui , Peter Zijlstra , Andy Lutomirski , Alexandre Ghiti , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev Subject: Re: [PATCH v5 4/4] entry: Inline syscall_exit_to_user_mode() Message-ID: References: <20250305-riscv_optimize_entry-v5-0-6507b5dff3ce@rivosinc.com> <20250305-riscv_optimize_entry-v5-4-6507b5dff3ce@rivosinc.com> <87senn3dh1.ffs@tglx> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87senn3dh1.ffs@tglx> On Sat, Mar 08, 2025 at 01:37:30PM +0100, Thomas Gleixner wrote: > On Wed, Mar 05 2025 at 16:43, Charlie Jenkins wrote: > > Architectures using the generic entry code can be optimized by having > > syscall_exit_to_user_mode inlined. > > That's a pretty handwavy claim. What's the actual benefit in numbers? I put the numbers in the cover letter! Here is the data I gathered: Testing was done with the byte-unixbench [1] syscall benchmark (which calls getpid) and QEMU. On riscv I measured a 7.09246% improvement, on x86 a 2.98843% improvement, on loongarch a 6.07954% improvement, and on s390 a 11.1328% improvement. The Intel bot also reported "kernel test robot noticed a 1.9% improvement of stress-ng.seek.ops_per_sec" [2] - Charlie > > Thanks, > > tglx