linux-kernel - Re: [PATCH net v3] net: Force inlining of checksum functions in net/checksum.h

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Date:   Fri, 18 Feb 2022 02:27:16 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...hat.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net v3] net: Force inlining of checksum functions in net/checksum.h

On Fri, Feb 18, 2022 at 1:49 AM David Laight <David.Laight@...lab.com> wrote:
>
> From: Masahiro Yamada
> > Sent: 17 February 2022 16:17
> ...
> > No.  Not that one.
> >
> > The commit you presumably want to revert is:
> >
> > a771f2b82aa2 ("[PATCH] Add a section about inlining to
> > Documentation/CodingStyle")
> >
> > This is now referred to as "__always_inline disease", though.
>
> That description is largely fine.
>
> Inappropriate 'inline' ought to be removed.
> Then 'inline' means - 'really do inline this'.


You cannot change "static inline" to "static"
in header files.

If  "static inline" meant __always_inline,
there would be no way to negate it.
That's why we need both inline and __always_inline.




> Anyone remember massive 100+ line #defines being
> used to get code inlined 'to make it faster'.
> Sometimes being expanded several times in succession.
> May have helped a 68020, but likely to be a loss on
> modern cpu with large I-cache and slow memory.
>
>         David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)


--
Best Regards
Masahiro Yamada