linux-kernel - Re: [PATCH v6 0/4] entry: Move ret_from_fork() to C and inline syscall_exit_to_user

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Message-ID: <87frj613kz.ffs@tglx>
Date: Fri, 21 Mar 2025 22:22:36 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Charlie Jenkins <charlie@...osinc.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Huacai
 Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>, Peter
 Zijlstra <peterz@...radead.org>, Andy Lutomirski <luto@...nel.org>,
 Alexandre Ghiti <alexghiti@...osinc.com>, Arnd Bergmann <arnd@...db.de>,
 Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 loongarch@...ts.linux.dev, Charlie Jenkins <charlie@...osinc.com>
Subject: Re: [PATCH v6 0/4] entry: Move ret_from_fork() to C and inline
 syscall_exit_to_user_mode()

On Thu, Mar 20 2025 at 10:29, Charlie Jenkins wrote:
> 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.

This looks sane now. I've bookmarked it as post-merge window material.

Thanks,

        tglx