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Message-Id: <20200116120230.16759-4-parth@linux.ibm.com>
Date: Thu, 16 Jan 2020 17:32:30 +0530
From: Parth Shah <parth@...ux.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: peterz@...radead.org, mingo@...hat.com, vincent.guittot@...aro.org,
patrick.bellasi@...bug.net, valentin.schneider@....com,
qais.yousef@....com, pavel@....cz, dhaval.giani@...cle.com,
qperret@...rret.net, David.Laight@...LAB.COM, pjt@...gle.com,
tj@...nel.org, dietmar.eggemann@....com
Subject: [PATCH v3 3/3] sched: Allow sched_{get,set}attr to change latency_nice of the task
Introduce the latency_nice attribute to sched_attr and provide a
mechanism to change the value with the use of sched_setattr/sched_getattr
syscall.
Also add new flag "SCHED_FLAG_LATENCY_NICE" to hint the change in
latency_nice of the task on every sched_setattr syscall.
Signed-off-by: Parth Shah <parth@...ux.ibm.com>
Reviewed-by: Qais Yousef <qais.yousef@....com>
---
include/uapi/linux/sched.h | 4 +++-
include/uapi/linux/sched/types.h | 19 +++++++++++++++++++
kernel/sched/core.c | 17 +++++++++++++++++
tools/include/uapi/linux/sched.h | 4 +++-
4 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
index 4a0217832464..88ce1e8d7553 100644
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -121,6 +121,7 @@ struct clone_args {
#define SCHED_FLAG_KEEP_PARAMS 0x10
#define SCHED_FLAG_UTIL_CLAMP_MIN 0x20
#define SCHED_FLAG_UTIL_CLAMP_MAX 0x40
+#define SCHED_FLAG_LATENCY_NICE 0x80
#define SCHED_FLAG_KEEP_ALL (SCHED_FLAG_KEEP_POLICY | \
SCHED_FLAG_KEEP_PARAMS)
@@ -132,6 +133,7 @@ struct clone_args {
SCHED_FLAG_RECLAIM | \
SCHED_FLAG_DL_OVERRUN | \
SCHED_FLAG_KEEP_ALL | \
- SCHED_FLAG_UTIL_CLAMP)
+ SCHED_FLAG_UTIL_CLAMP | \
+ SCHED_FLAG_LATENCY_NICE)
#endif /* _UAPI_LINUX_SCHED_H */
diff --git a/include/uapi/linux/sched/types.h b/include/uapi/linux/sched/types.h
index c852153ddb0d..626ab61c1145 100644
--- a/include/uapi/linux/sched/types.h
+++ b/include/uapi/linux/sched/types.h
@@ -10,6 +10,7 @@ struct sched_param {
#define SCHED_ATTR_SIZE_VER0 48 /* sizeof first published struct */
#define SCHED_ATTR_SIZE_VER1 56 /* add: util_{min,max} */
+#define SCHED_ATTR_SIZE_VER2 60 /* add: latency_nice */
/*
* Extended scheduling parameters data structure.
@@ -96,6 +97,22 @@ struct sched_param {
* on a CPU with a capacity big enough to fit the specified value.
* A task with a max utilization value smaller than 1024 is more likely
* scheduled on a CPU with no more capacity than the specified value.
+ *
+ * Latency Tolerance Attributes
+ * ===========================
+ *
+ * A subset of sched_attr attributes allows to specify the relative latency
+ * requirements of a task with respect to the other tasks running/queued in the
+ * system.
+ *
+ * @ sched_latency_nice task's latency_nice value
+ *
+ * The latency_nice of a task can have any value in a range of
+ * [LATENCY_NICE_MIN..LATENCY_NICE_MAX].
+ *
+ * A task with latency_nice with the value of LATENCY_NICE_MIN can be
+ * taken for a task with lower latency requirements as opposed to the task with
+ * higher latency_nice.
*/
struct sched_attr {
__u32 size;
@@ -118,6 +135,8 @@ struct sched_attr {
__u32 sched_util_min;
__u32 sched_util_max;
+ /* latency requirement hints */
+ __s32 sched_latency_nice;
};
#endif /* _UAPI_LINUX_SCHED_TYPES_H */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a7359836bf17..a9e5d157b1a5 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4713,6 +4713,8 @@ static void __setscheduler_params(struct task_struct *p,
p->rt_priority = attr->sched_priority;
p->normal_prio = normal_prio(p);
set_load_weight(p, true);
+
+ p->latency_nice = attr->sched_latency_nice;
}
/* Actually do priority change: must hold pi & rq lock. */
@@ -4870,6 +4872,13 @@ static int __sched_setscheduler(struct task_struct *p,
return retval;
}
+ if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE) {
+ if (attr->sched_latency_nice > MAX_LATENCY_NICE)
+ return -EINVAL;
+ if (attr->sched_latency_nice < MIN_LATENCY_NICE)
+ return -EINVAL;
+ }
+
if (pi)
cpuset_read_lock();
@@ -4904,6 +4913,9 @@ static int __sched_setscheduler(struct task_struct *p,
goto change;
if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
goto change;
+ if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE &&
+ attr->sched_latency_nice != p->latency_nice)
+ goto change;
p->sched_reset_on_fork = reset_on_fork;
retval = 0;
@@ -5152,6 +5164,9 @@ static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *a
size < SCHED_ATTR_SIZE_VER1)
return -EINVAL;
+ if ((attr->sched_flags & SCHED_FLAG_LATENCY_NICE) &&
+ size < SCHED_ATTR_SIZE_VER2)
+ return -EINVAL;
/*
* XXX: Do we want to be lenient like existing syscalls; or do we want
* to be strict and return an error on out-of-bounds values?
@@ -5381,6 +5396,8 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
else
kattr.sched_nice = task_nice(p);
+ kattr.sched_latency_nice = p->latency_nice;
+
#ifdef CONFIG_UCLAMP_TASK
kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
diff --git a/tools/include/uapi/linux/sched.h b/tools/include/uapi/linux/sched.h
index 4a0217832464..fa67e2527169 100644
--- a/tools/include/uapi/linux/sched.h
+++ b/tools/include/uapi/linux/sched.h
@@ -121,6 +121,7 @@ struct clone_args {
#define SCHED_FLAG_KEEP_PARAMS 0x10
#define SCHED_FLAG_UTIL_CLAMP_MIN 0x20
#define SCHED_FLAG_UTIL_CLAMP_MAX 0x40
+#define SCHED_FLAG_LATENCY_NICE 0X80
#define SCHED_FLAG_KEEP_ALL (SCHED_FLAG_KEEP_POLICY | \
SCHED_FLAG_KEEP_PARAMS)
@@ -132,6 +133,7 @@ struct clone_args {
SCHED_FLAG_RECLAIM | \
SCHED_FLAG_DL_OVERRUN | \
SCHED_FLAG_KEEP_ALL | \
- SCHED_FLAG_UTIL_CLAMP)
+ SCHED_FLAG_UTIL_CLAMP | \
+ SCHED_FLAG_LATENCY_NICE)
#endif /* _UAPI_LINUX_SCHED_H */
--
2.17.2
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