Re: [PATCH 2/3] sched, timer: Use atomics for thread_group_cputimer to improve scalability

[Ingo Molnar <mingo@kernel.org>]

* Ingo Molnar <mingo@kernel.org> wrote:

> So after your changes we still have a separate:
> 
> struct task_cputime {
>         cputime_t utime;
>         cputime_t stime;
>         unsigned long long sum_exec_runtime;
> };
> 
> Which then weirdly overlaps with a different structure on a different 
> abstraction level:
> 
>  struct thread_group_cputimer {
> 	atomic64_t utime;
> 	atomic64_t stime;
> 	atomic64_t sum_exec_runtime;
>  	int running;
>  };
> 
> So I think it would be more obvious what's going on if we introduced 
> an atomic task_cputime structure:
> 
>  struct task_cputime_atomic {
> 	atomic64_t utime;
> 	atomic64_t stime;
> 	atomic64_t sum_exec_runtime;
>  };
> 
> and put that into 'struct thread_group_cputimer':
> 
>  struct thread_group_cputimer {
> 	struct task_cputime_atomic cputime_atomic;
>   	int running;
>  };
> 
> Maybe even factor out the main update and reading methods into 
> expressively named helper inlines?

Btw., feel free to preserve your original series and turn this 
factoring out into 1-2 extra patches on top of it: so that we preserve 
your testing on the original series, and see the structure (and cost) 
of the factoring out of the new data type.

Thanks,

	Ingo