On Wed, May 29, 2019 at 08:36:47PM +0000, Vineeth Remanan Pillai wrote:
> From: Peter Zijlstra <pet...@infradead.org>
>
> Introduce task_struct::core_cookie as an opaque identifier for core
> scheduling. When enabled; core scheduling will only allow matching
> task to be on the core; where idle matches everything.
>
> When task_struct::core_cookie is set (and core scheduling is enabled)
> these tasks are indexed in a second RB-tree, first on cookie value
> then on scheduling function, such that matching task selection always
> finds the most elegible match.
>
> NOTE: *shudder* at the overhead...
>
> NOTE: *sigh*, a 3rd copy of the scheduling function; the alternative
> is per class tracking of cookies and that just duplicates a lot of
> stuff for no raisin (the 2nd copy lives in the rt-mutex PI code).
s/raisen/reason
>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
> Signed-off-by: Vineeth Remanan Pillai <vpil...@digitalocean.com>
> Signed-off-by: Julien Desfossez <jdesfos...@digitalocean.com>
> ---
>
> Changes in v3
> -------------
> - Refactored priority comparison code
> - Fixed a comparison logic issue in sched_core_find
> - Aaron Lu
>
> Changes in v2
> -------------
> - Improves the priority comparison logic between processes in
> different cpus.
> - Peter Zijlstra
> - Aaron Lu
>
> ---
> include/linux/sched.h | 8 ++-
> kernel/sched/core.c | 146 ++++++++++++++++++++++++++++++++++++++++++
> kernel/sched/fair.c | 46 -------------
> kernel/sched/sched.h | 55 ++++++++++++++++
> 4 files changed, 208 insertions(+), 47 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 1549584a1538..a4b39a28236f 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -636,10 +636,16 @@ struct task_struct {
> const struct sched_class *sched_class;
> struct sched_entity se;
> struct sched_rt_entity rt;
> + struct sched_dl_entity dl;
> +
> +#ifdef CONFIG_SCHED_CORE
> + struct rb_node core_node;
> + unsigned long core_cookie;
> +#endif
> +
> #ifdef CONFIG_CGROUP_SCHED
> struct task_group *sched_task_group;
> #endif
> - struct sched_dl_entity dl;
>
> #ifdef CONFIG_PREEMPT_NOTIFIERS
> /* List of struct preempt_notifier: */
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index b1ce33f9b106..112d70f2b1e5 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -64,6 +64,141 @@ int sysctl_sched_rt_runtime = 950000;
>
> DEFINE_STATIC_KEY_FALSE(__sched_core_enabled);
>
> +/* kernel prio, less is more */
> +static inline int __task_prio(struct task_struct *p)
> +{
> + if (p->sched_class == &stop_sched_class) /* trumps deadline */
> + return -2;
> +
> + if (rt_prio(p->prio)) /* includes deadline */
> + return p->prio; /* [-1, 99] */
> +
> + if (p->sched_class == &idle_sched_class)
> + return MAX_RT_PRIO + NICE_WIDTH; /* 140 */
> +
> + return MAX_RT_PRIO + MAX_NICE; /* 120, squash fair */
> +}
> +
> +/*
> + * l(a,b)
> + * le(a,b) := !l(b,a)
> + * g(a,b) := l(b,a)
> + * ge(a,b) := !l(a,b)
why does this truth table comment exist?
maybe inline comments at the confusing inequalities would be better.
--mark
