Task can set its latency priority with sched_setattr(), which is then used
to set the latency offset of its sched_enity, but sched group entities
still have the default latency offset value.
Add a latency.nice field in cpu cgroup controller to set the latency
priority of the group similarly to sched_setattr(). The latency priority
is then used to set the offset of the sched_entities of the group.
Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
---
Documentation/admin-guide/cgroup-v2.rst | 10 ++++++++
kernel/sched/core.c | 30 +++++++++++++++++++++++
kernel/sched/fair.c | 32 +++++++++++++++++++++++++
kernel/sched/sched.h | 4 ++++
4 files changed, 76 insertions(+)
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 1b3ed1c3b3f1..c08424593e4a 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1121,6 +1121,16 @@ All time durations are in microseconds.
values similar to the sched_setattr(2). This maximum utilization
value is used to clamp the task specific maximum utilization clamp.
+ cpu.latency.nice
+ A read-write single value file which exists on non-root
+ cgroups. The default is "0".
+
+ The nice value is in the range [-20, 19].
+
+ This interface file allows reading and setting latency using the
+ same values used by sched_setattr(2). The latency_nice of a group is
+ used to limit the impact of the latency_nice of a task outside the
+ group.
Memory
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d5b7e237d79b..093cc1af73dc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -11059,6 +11059,25 @@ static int cpu_idle_write_s64(struct cgroup_subsys_state *css,
{
return sched_group_set_idle(css_tg(css), idle);
}
+
+static s64 cpu_latency_nice_read_s64(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ return LATENCY_TO_NICE(css_tg(css)->latency_prio);
+}
+
+static int cpu_latency_nice_write_s64(struct cgroup_subsys_state *css,
+ struct cftype *cft, s64 nice)
+{
+ int prio;
+
+ if (nice < MIN_LATENCY_NICE || nice > MAX_LATENCY_NICE)
+ return -ERANGE;
+
+ prio = NICE_TO_LATENCY(nice);
+
+ return sched_group_set_latency(css_tg(css), prio);
+}
#endif
static struct cftype cpu_legacy_files[] = {
@@ -11073,6 +11092,11 @@ static struct cftype cpu_legacy_files[] = {
.read_s64 = cpu_idle_read_s64,
.write_s64 = cpu_idle_write_s64,
},
+ {
+ .name = "latency.nice",
+ .read_s64 = cpu_latency_nice_read_s64,
+ .write_s64 = cpu_latency_nice_write_s64,
+ },
#endif
#ifdef CONFIG_CFS_BANDWIDTH
{
@@ -11290,6 +11314,12 @@ static struct cftype cpu_files[] = {
.read_s64 = cpu_idle_read_s64,
.write_s64 = cpu_idle_write_s64,
},
+ {
+ .name = "latency.nice",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .read_s64 = cpu_latency_nice_read_s64,
+ .write_s64 = cpu_latency_nice_write_s64,
+ },
#endif
#ifdef CONFIG_CFS_BANDWIDTH
{
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 414b6243208b..dc7570f43ebe 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12274,6 +12274,7 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
goto err;
tg->shares = NICE_0_LOAD;
+ tg->latency_prio = DEFAULT_LATENCY_PRIO;
init_cfs_bandwidth(tg_cfs_bandwidth(tg));
@@ -12372,6 +12373,9 @@ void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
}
se->my_q = cfs_rq;
+
+ se->latency_offset = calc_latency_offset(tg->latency_prio);
+
/* guarantee group entities always have weight */
update_load_set(&se->load, NICE_0_LOAD);
se->parent = parent;
@@ -12502,6 +12506,34 @@ int sched_group_set_idle(struct task_group *tg, long idle)
return 0;
}
+int sched_group_set_latency(struct task_group *tg, int prio)
+{
+ long latency_offset;
+ int i;
+
+ if (tg == &root_task_group)
+ return -EINVAL;
+
+ mutex_lock(&shares_mutex);
+
+ if (tg->latency_prio == prio) {
+ mutex_unlock(&shares_mutex);
+ return 0;
+ }
+
+ tg->latency_prio = prio;
+ latency_offset = calc_latency_offset(prio);
+
+ for_each_possible_cpu(i) {
+ struct sched_entity *se = tg->se[i];
+
+ WRITE_ONCE(se->latency_offset, latency_offset);
+ }
+
+ mutex_unlock(&shares_mutex);
+ return 0;
+}
+
#else /* CONFIG_FAIR_GROUP_SCHED */
void free_fair_sched_group(struct task_group *tg) { }
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3f42f86105d4..9a2e71231083 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -378,6 +378,8 @@ struct task_group {
/* A positive value indicates that this is a SCHED_IDLE group. */
int idle;
+ /* latency priority of the group. */
+ int latency_prio;
#ifdef CONFIG_SMP
/*
@@ -488,6 +490,8 @@ extern int sched_group_set_shares(struct task_group *tg, unsigned long shares);
extern int sched_group_set_idle(struct task_group *tg, long idle);
+extern int sched_group_set_latency(struct task_group *tg, int prio);
+
#ifdef CONFIG_SMP
extern void set_task_rq_fair(struct sched_entity *se,
struct cfs_rq *prev, struct cfs_rq *next);
--
2.34.1
