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Message-ID: <CAHp75VcZgkuOA3pSrg7cN36EAB4Y0jV2xFNfj-sGp_C17J2yAQ@mail.gmail.com>
Date: Sat, 28 Jan 2023 21:54:44 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: David Laight <David.Laight@...lab.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Kees Cook <keescook@...omium.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Andy Shevchenko <andy@...nel.org>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v1 1/1] lib/string: Use strchr() in strpbrk()
On Sat, Jan 28, 2023 at 4:51 PM David Laight <David.Laight@...lab.com> wrote:
>
> From: Andy Shevchenko
> > Sent: 27 January 2023 15:52
> >
> > Use strchr() instead of open coding it as it's done elsewhere in
> > the same file. Either we will have similar to what it was or possibly
> > better performance in case architecture implements its own strchr().
>
> Except that you get a whole load of calls to strchr() for (typically)
> very few characters.
> So the cost of the calls dominates, anything that tries to speed up
> strchr() for long strings will also slow things down.
Hmm... I haven't seen the calls, I assume gcc simply inlined a copy of that.
...
> Although I very much doubt strpbrk() is used anywhere where
> performance matters.
strsep()/strspn() are the users.
--
With Best Regards,
Andy Shevchenko
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