linux-hardening - Re: [PATCH v2 00/14] riscv: optimize string functions and add kunit tests

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Message-ID: <aWYHzYRdba03HSIH@smile.fi.intel.com>
Date: Tue, 13 Jan 2026 10:52:29 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Feng Jiang <jiangfeng@...inos.cn>
Cc: pjw@...nel.org, palmer@...belt.com, aou@...s.berkeley.edu,
	alex@...ti.fr, kees@...nel.org, andy@...nel.org,
	akpm@...ux-foundation.org, ebiggers@...nel.org,
	martin.petersen@...cle.com, ardb@...nel.org,
	ajones@...tanamicro.com, conor.dooley@...rochip.com,
	samuel.holland@...ive.com, linus.walleij@...aro.org,
	nathan@...nel.org, linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 00/14] riscv: optimize string functions and add kunit
 tests

On Tue, Jan 13, 2026 at 04:27:34PM +0800, Feng Jiang wrote:
> This series introduces optimized assembly implementations for strnlen,
> strchr, and strrchr on the RISC-V architecture. To support a rigorous
> verification process, the series also significantly expands the
> string_kunit test suite with both functional correctness tests and
> performance benchmarks.
> 
> The patchset is organized as follows:
> - Refactoring (Patches 1-4): Extract generic C implementations for
>   strlen, strnlen, strchr, and strrchr into exported __generic_* functions.
> - Correctness Testing (Patches 5-7): Extend string_kunit with detailed
>   functional tests for the target functions.
> - Performance Benchmarking (Patches 8-11): Add a benchmarking framework
>   to string_kunit to measure execution time across various string lengths.
> - RISC-V Optimizations (Patches 12-14): Provide the optimized assembly
>   implementations for the RISC-V architecture.

...

>         # string_test_strlen_bench: strlen performance (long, len: 2048, iters: 10000):
>         # string_test_strlen_bench:   arch-optimized: 14100 ns
>         # string_test_strlen_bench:   generic C:      35605600 ns
>         # string_test_strlen_bench:   speedup:        2525.21x

Doesn't sound right. I think you measured cache performance and not your algo.

-- 
With Best Regards,
Andy Shevchenko