Messages in this thread Patch in this message | | | From | Parth Shah <> | Subject | [PATCH v5 1/4] sched: Introduce latency-nice as a per-task attribute | Date | Fri, 28 Feb 2020 14:37:52 +0530 |
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Latency-nice indicates the latency requirements of a task with respect to the other tasks in the system. The value of the attribute can be within the range of [-20, 19] both inclusive to be in-line with the values just like task nice values.
latency_nice = -20 indicates the task to have the least latency as compared to the tasks having latency_nice = +19.
The latency_nice may affect only the CFS SCHED_CLASS by getting latency requirements from the userspace.
Additionally, add debugging bits for newly added latency_nice attribute.
Signed-off-by: Parth Shah <parth@linux.ibm.com> Reviewed-by: Qais Yousef <qais.yousef@arm.com> --- include/linux/sched.h | 1 + kernel/sched/debug.c | 1 + kernel/sched/sched.h | 18 ++++++++++++++++++ 3 files changed, 20 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h index 2e9199bf947b..cf23c147dd36 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -679,6 +679,7 @@ struct task_struct { int static_prio; int normal_prio; unsigned int rt_priority; + int latency_nice; const struct sched_class *sched_class; struct sched_entity se; diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 8331bc04aea2..2a96dadc9752 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -958,6 +958,7 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns, #endif P(policy); P(prio); + P(latency_nice); if (task_has_dl_policy(p)) { P(dl.runtime); P(dl.deadline); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 2a0caf394dd4..a857e1baebd7 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -101,6 +101,24 @@ extern long calc_load_fold_active(struct rq *this_rq, long adjust); */ #define NS_TO_JIFFIES(TIME) ((unsigned long)(TIME) / (NSEC_PER_SEC / HZ)) +/* + * Latency nice is meant to provide scheduler hints about the relative + * latency requirements of a task with respect to other tasks. + * Thus a task with latency_nice == 19 can be hinted as the task with no + * latency requirements, in contrast to the task with latency_nice == -20 + * which should be given priority in terms of lower latency. + */ +#define MAX_LATENCY_NICE 19 +#define MIN_LATENCY_NICE -20 + +#define LATENCY_NICE_WIDTH \ + (MAX_LATENCY_NICE - MIN_LATENCY_NICE + 1) + +/* + * Default tasks should be treated as a task with latency_nice = 0. + */ +#define DEFAULT_LATENCY_NICE 0 + /* * Increase resolution of nice-level calculations for 64-bit architectures. * The extra resolution improves shares distribution and load balancing of -- 2.17.2
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