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

Ingo Molnar
2015-04-15T07:35:44Z

* 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