[PATCH v6 0/4] entry: Move ret_from_fork() to C and inline syscall_exit_to_user_mode()

From: Charlie Jenkins <charlie@rivosinc.com>
To: Paul Walmsley <paul.walmsley@sifive.com>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Huacai Chen <chenhuacai@kernel.org>,
	 WANG Xuerui <kernel@xen0n.name>,
	Thomas Gleixner <tglx@linutronix.de>,
	 Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	 Alexandre Ghiti <alexghiti@rivosinc.com>,
	Arnd Bergmann <arnd@arndb.de>,  Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	 loongarch@lists.linux.dev,
	Charlie Jenkins <charlie@rivosinc.com>
Subject: [PATCH v6 0/4] entry: Move ret_from_fork() to C and inline syscall_exit_to_user_mode()
Date: Thu, 20 Mar 2025 10:29:20 -0700	[thread overview]
Message-ID: <20250320-riscv_optimize_entry-v6-0-63e187e26041@rivosinc.com> (raw)

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.

The Intel bot also reported "kernel test robot noticed a 1.9%
improvement of stress-ng.seek.ops_per_sec" [2]

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
[2] https://lore.kernel.org/linux-riscv/202502051555.85ae6844-lkp@intel.com/

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
Changes in v6:
- Update commit message of patch 4 to contain performance numbers
- Link to v5: https://lore.kernel.org/r/20250305-riscv_optimize_entry-v5-0-6507b5dff3ce@rivosinc.com

Changes in v5:
- Rebase on 6.14-rc5
- Link to v4: https://lore.kernel.org/r/20250127-riscv_optimize_entry-v4-0-868cf7702dc9@rivosinc.com

Changes in v4:
- I had messed up warning for ct_state() on rebase, correct that issue
- Link to v3: https://lore.kernel.org/r/20250124-riscv_optimize_entry-v3-0-869f36b9e43b@rivosinc.com

Changes in v3:
- Fixup comment to properly reflect args (Alex)
- Fix prototypes for loongarch (Huacai)
- Link to v2: https://lore.kernel.org/r/20250123-riscv_optimize_entry-v2-0-7c259492d508@rivosinc.com

Changes in v2:
- Fixup compilation issues for loongarch
- Fixup compilation issues with CONFIG_CONTEXT_TRACKING_USER
- Link to v1: https://lore.kernel.org/r/20250122-riscv_optimize_entry-v1-0-4ee95559cfd0@rivosinc.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/asm-prototypes.h |  8 +++++
 arch/loongarch/kernel/entry.S               | 22 ++++++-------
 arch/loongarch/kernel/process.c             | 33 +++++++++++++++----
 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, 119 insertions(+), 79 deletions(-)
---
base-commit: 7eb172143d5508b4da468ed59ee857c6e5e01da6
change-id: 20240402-riscv_optimize_entry-583843420325
-- 
- Charlie

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