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Subject[RFC PATCH 1/9] sched,cgroup: Add interface for latency-nice
Date
Add Cgroup interface for latency-nice. Each CPU Cgroup adds a new file
"latency-nice" which is shared by all the threads in that Cgroup.

Signed-off-by: subhra mazumdar <subhra.mazumdar@oracle.com>
---
include/linux/sched.h | 1 +
kernel/sched/core.c | 40 ++++++++++++++++++++++++++++++++++++++++
kernel/sched/fair.c | 1 +
kernel/sched/sched.h | 8 ++++++++
4 files changed, 50 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1183741..b4a79c3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -631,6 +631,7 @@ struct task_struct {
int static_prio;
int normal_prio;
unsigned int rt_priority;
+ u64 latency_nice;

const struct sched_class *sched_class;
struct sched_entity se;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 874c427..47969bc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5976,6 +5976,7 @@ void __init sched_init(void)
init_dl_rq(&rq->dl);
#ifdef CONFIG_FAIR_GROUP_SCHED
root_task_group.shares = ROOT_TASK_GROUP_LOAD;
+ root_task_group.latency_nice = LATENCY_NICE_DEFAULT;
INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
/*
@@ -6345,6 +6346,7 @@ static void sched_change_group(struct task_struct *tsk, int type)
*/
tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
struct task_group, css);
+ tsk->latency_nice = tg->latency_nice;
tg = autogroup_task_group(tsk, tg);
tsk->sched_task_group = tg;

@@ -6812,6 +6814,34 @@ static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
}
#endif /* CONFIG_RT_GROUP_SCHED */

+static u64 cpu_latency_nice_read_u64(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ struct task_group *tg = css_tg(css);
+
+ return tg->latency_nice;
+}
+
+static int cpu_latency_nice_write_u64(struct cgroup_subsys_state *css,
+ struct cftype *cft, u64 latency_nice)
+{
+ struct task_group *tg = css_tg(css);
+ struct css_task_iter it;
+ struct task_struct *p;
+
+ if (latency_nice < LATENCY_NICE_MIN || latency_nice > LATENCY_NICE_MAX)
+ return -ERANGE;
+
+ tg->latency_nice = latency_nice;
+
+ css_task_iter_start(css, 0, &it);
+ while ((p = css_task_iter_next(&it)))
+ p->latency_nice = latency_nice;
+ css_task_iter_end(&it);
+
+ return 0;
+}
+
static struct cftype cpu_legacy_files[] = {
#ifdef CONFIG_FAIR_GROUP_SCHED
{
@@ -6848,6 +6878,11 @@ static struct cftype cpu_legacy_files[] = {
.write_u64 = cpu_rt_period_write_uint,
},
#endif
+ {
+ .name = "latency-nice",
+ .read_u64 = cpu_latency_nice_read_u64,
+ .write_u64 = cpu_latency_nice_write_u64,
+ },
{ } /* Terminate */
};

@@ -7015,6 +7050,11 @@ static struct cftype cpu_files[] = {
.write = cpu_max_write,
},
#endif
+ {
+ .name = "latency-nice",
+ .read_u64 = cpu_latency_nice_read_u64,
+ .write_u64 = cpu_latency_nice_write_u64,
+ },
{ } /* terminate */
};

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f35930f..b08d00c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10479,6 +10479,7 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
goto err;

tg->shares = NICE_0_LOAD;
+ tg->latency_nice = LATENCY_NICE_DEFAULT;

init_cfs_bandwidth(tg_cfs_bandwidth(tg));

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index b52ed1a..365c928 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -143,6 +143,13 @@ static inline void cpu_load_update_active(struct rq *this_rq) { }
#define NICE_0_LOAD (1L << NICE_0_LOAD_SHIFT)

/*
+ * Latency-nice default value
+ */
+#define LATENCY_NICE_DEFAULT 5
+#define LATENCY_NICE_MIN 1
+#define LATENCY_NICE_MAX 100
+
+/*
* Single value that decides SCHED_DEADLINE internal math precision.
* 10 -> just above 1us
* 9 -> just above 0.5us
@@ -362,6 +369,7 @@ struct cfs_bandwidth {
/* Task group related information */
struct task_group {
struct cgroup_subsys_state css;
+ u64 latency_nice;

#ifdef CONFIG_FAIR_GROUP_SCHED
/* schedulable entities of this group on each CPU */
--
2.9.3
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