From: Parth Shah <parth@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
[rebase, move defines in sched/prio.h]
Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
---
include/linux/sched.h | 1 +
include/linux/sched/prio.h | 18 ++++++++++++++++++
kernel/sched/debug.c | 1 +
3 files changed, 20 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4df2b3e76b30..6c61bde49152 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -784,6 +784,7 @@ struct task_struct {
int static_prio;
int normal_prio;
unsigned int rt_priority;
+ int latency_nice;
struct sched_entity se;
struct sched_rt_entity rt;
diff --git a/include/linux/sched/prio.h b/include/linux/sched/prio.h
index ab83d85e1183..bfcd7f1d1e11 100644
--- a/include/linux/sched/prio.h
+++ b/include/linux/sched/prio.h
@@ -42,4 +42,22 @@ static inline long rlimit_to_nice(long prio)
return (MAX_NICE - prio + 1);
}
+/*
+ * 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
+
#endif /* _LINUX_SCHED_PRIO_H */
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 1637b65ba07a..68be7a3e42a3 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -1043,6 +1043,7 @@ 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);
--
2.34.1
