Re: [PATCH] vsprintf: uninline simple_strntoull(), reorder arguments

[Petr Mladek]

On Fri 2023-10-27 17:13:58, Alexey Dobriyan wrote:
> * uninline simple_strntoull(),
>   gcc overinlines and this function is not performance critical
> 
> * reorder arguments, so that appending INT_MAX as 4th argument
>   generates very efficient tail call
> 
> Space savings:
> 
> 	add/remove: 1/0 grow/shrink: 0/3 up/down: 27/-179 (-152)
> 	Function                            old     new   delta
> 	simple_strntoll                       -      27     +27
> 	simple_strtoull                      15      10      -5
> 	simple_strtoll                       41       7     -34
> 	vsscanf                            1930    1790    -140
> 
> Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>

I am usually quite skeptical about these micro-optimizations. They might
help only on some architectures with some compiler versions. And
they might make it worse for others.

Well, I could imagine that passing constant via the last parameter
might help in most cases. And the new ordering of the parameters
is fine. So let's get it in.

Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>

I have just pushed the patch into printk/linux.git, branch for-6.7.

Best Regards,
Petr