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From: Parth Shah <parth@linux.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: peterz@infradead.org, mingo@redhat.com,
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
	qais.yousef@arm.com, chris.hyser@oracle.com,
	patrick.bellasi@matbug.net, valentin.schneider@arm.com,
	David.Laight@ACULAB.COM, pjt@google.com, pavel@ucw.cz,
	tj@kernel.org, dhaval.giani@oracle.com, qperret@google.com,
	tim.c.chen@linux.intel.com
Subject: [PATCH v4 3/4] sched: Allow sched_{get,set}attr to change latency_nice of the task
Date: Mon, 24 Feb 2020 14:29:17 +0530	[thread overview]
Message-ID: <20200224085918.16955-4-parth@linux.ibm.com> (raw)
In-Reply-To: <20200224085918.16955-1-parth@linux.ibm.com>

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@linux.ibm.com>
Reviewed-by: Qais Yousef <qais.yousef@arm.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 65b6c00d6dac..e1dc536d4ca3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4723,6 +4723,8 @@ 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. */
@@ -4880,6 +4882,13 @@ 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();
 
@@ -4914,6 +4923,9 @@ 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;
@@ -5162,6 +5174,9 @@ 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?
@@ -5391,6 +5406,8 @@ 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


  parent reply	other threads:[~2020-02-24  8:59 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-24  8:59 [PATCH v4 0/4] Introduce per-task latency_nice for scheduler hints Parth Shah
2020-02-24  8:59 ` [PATCH v4 1/4] sched: Introduce latency-nice as a per-task attribute Parth Shah
2020-02-24  8:59 ` [PATCH v4 2/4] sched/core: Propagate parent task's latency requirements to the child task Parth Shah
2020-02-25  6:32   ` Pavan Kondeti
2020-02-25  8:16     ` Parth Shah
2020-02-24  8:59 ` Parth Shah [this message]
2020-02-25  6:54   ` [PATCH v4 3/4] sched: Allow sched_{get,set}attr to change latency_nice of the task Pavan Kondeti
2020-02-25 15:03     ` Parth Shah
2020-02-26  3:44       ` Pavan Kondeti
2020-02-24  8:59 ` [PATCH v4 4/4] sched/core: Add permission checks for setting the latency_nice value Parth Shah
2020-02-24 13:29   ` Qais Yousef
2020-02-25  6:47     ` Parth Shah
2020-02-27 11:44       ` Qais Yousef
2020-02-27 14:46         ` chris hyser
2020-02-24 23:08   ` chris hyser

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