Re: [PATCH sched_ext/for-6.11] sched, sched_ext: Replace scx_next_task_picked() with sched_class->switch_class()

[Tejun Heo]

Hello,

On Thu, Jun 20, 2024 at 03:42:48PM -0700, Linus Torvalds wrote:
...
> Btw, indirect calls are now expensive enough that when you have only a
> handful of choices, instead of a variable
> 
>         class->some_callback(some_arguments);
> 
> you might literally be better off with a macro that does
> 
>        #define call_sched_fn(class, name, arg...) switch (class) { \
>         case &fair_name_class: fair_name_class.name(arg); break; \
>         ... unroll them all here..
> 
> which then just generates a (very small) tree of if-statements.
> 
> Again, this is entirely too ugly to do unless people *really* care.
> But for situations where you have a small handful of cases known at
> compile-time, it's not out of the question, and it probably does
> generate better code.

I'll update the patch description to point to the previous message just in
case and apply it to sched_ext/for-6.11.

Thanks.

-- 
tejun