linux-kernel - Re: [PATCH 1/2] lib/string: Improve strstarts() performance

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Message-ID: <0e603b02-b272-4bcc-8b86-1a3dca9477d7@icloud.com>
Date: Mon, 7 Apr 2025 22:33:34 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Andy Shevchenko <andy@...nel.org>
Cc: Kees Cook <kees@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>,
 linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
 Zijun Hu <quic_zijuhu@...cinc.com>, "Rob Herring (Arm)" <robh@...nel.org>
Subject: Re: [PATCH 1/2] lib/string: Improve strstarts() performance

On 2025/4/7 21:51, Andy Shevchenko wrote:
> First of all, this function is supposed to be run against constant string literals.

for strstarts(s, "prefix"), strlen("prefix") should *NOT* be compile
time constant. it is a loop and unavoidable to have strlen("prefix")
iterations.

> Second, this commit message has zero proofs to tell if there is actual performance
> downgrage even in the case when prefix is not a constant string literal.

for either constant string or non constant string. this patch
eliminating a loop which have strlen()iterations. i feel it is obvious
it can improve performance.