On Fri, Feb 18, 2022 at 12:15 AM David Laight [off-list ref] wrote:

From: Christophe Leroy

quoted

Sent: 17 February 2022 14:55

Le 17/02/2022 à 15:50, Christophe Leroy a écrit :

quoted

Adding Ingo, Andrew and Nick as they were involved in the subjet,

Le 17/02/2022 à 14:36, David Laight a écrit :

quoted

From: Christophe Leroy

quoted

Sent: 17 February 2022 12:19

All functions defined as static inline in net/checksum.h are
meant to be inlined for performance reason.

But since commit ac7c3e4ff401 ("compiler: enable
CONFIG_OPTIMIZE_INLINING forcibly") the compiler is allowed to
uninline functions when it wants.

Fair enough in the general case, but for tiny performance critical
checksum helpers that's counter-productive.

There isn't a real justification for allowing the compiler
to 'not inline' functions in that commit.

Do you mean that the two following commits should be reverted:

- 889b3c1245de ("compiler: remove CONFIG_OPTIMIZE_INLINING entirely")
- 4c4e276f6491 ("net: Force inlining of checksum functions in
net/checksum.h")

Of course not the above one (copy/paste error), but:
- ac7c3e4ff401 ("compiler: enable CONFIG_OPTIMIZE_INLINING forcibly")

That's the one I looked at.

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.




CONFIG_OPTIMIZE_INLINING has 14 years of history for x86.
See commit 60a3cdd06394 ("x86: add optimized inlining").
We always give gcc freedom to not inline functions marked as inline.




-- 
Best Regards
Masahiro Yamada