linux-kernel - [PATCH 0/4] entry: Move ret_from_fork() to C and inline syscall_exit_to_user

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Message-Id: <20250122-riscv_optimize_entry-v1-0-4ee95559cfd0@rivosinc.com>
Date: Wed, 22 Jan 2025 14:56:19 -0800
From: Charlie Jenkins <charlie@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Huacai Chen <chenhuacai@...nel.org>, 
 WANG Xuerui <kernel@...0n.name>, Thomas Gleixner <tglx@...utronix.de>, 
 Peter Zijlstra <peterz@...radead.org>, Andy Lutomirski <luto@...nel.org>, 
 Alexandre Ghiti <alexghiti@...osinc.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 loongarch@...ts.linux.dev, Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH 0/4] entry: Move ret_from_fork() to C and inline
 syscall_exit_to_user_mode()

Similar to commit 221a164035fd ("entry: Move
syscall_enter_from_user_mode() to header file"), move
syscall_exit_to_user_mode() to the header file as well.

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.

Since this is on QEMU, I know these numbers are not perfect, but they
show a trend of general improvement across all architectures that use
the generic entry code.

[1] https://github.com/kdlucas/byte-unixbench

Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
Charlie Jenkins (4):
      riscv: entry: Convert ret_from_fork() to C
      riscv: entry: Split ret_from_fork() into user and kernel
      loongarch: entry: Migrate ret_from_fork() to C
      entry: Inline syscall_exit_to_user_mode()

 arch/loongarch/include/asm/switch_to.h  |  8 ++++++
 arch/loongarch/kernel/entry.S           | 22 +++++++--------
 arch/loongarch/kernel/process.c         | 36 ++++++++++++++++++++----
 arch/riscv/include/asm/asm-prototypes.h |  2 ++
 arch/riscv/kernel/entry.S               | 20 ++++++++------
 arch/riscv/kernel/process.c             | 21 ++++++++++++--
 include/linux/entry-common.h            | 43 +++++++++++++++++++++++++++--
 kernel/entry/common.c                   | 49 +--------------------------------
 8 files changed, 122 insertions(+), 79 deletions(-)
---
base-commit: ffd294d346d185b70e28b1a28abe367bbfe53c04
change-id: 20240402-riscv_optimize_entry-583843420325
-- 
- Charlie