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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 1/4] sched: Introduce latency-nice as a per-task attribute
Date: Mon, 24 Feb 2020 14:29:15 +0530	[thread overview]
Message-ID: <20200224085918.16955-2-parth@linux.ibm.com> (raw)
In-Reply-To: <20200224085918.16955-1-parth@linux.ibm.com>

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.

Signed-off-by: Parth Shah <parth@linux.ibm.com>
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
---
 include/linux/sched.h |  1 +
 kernel/sched/sched.h  | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 467d26046416..0668948fddcd 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -676,6 +676,7 @@ struct task_struct {
 	int				static_prio;
 	int				normal_prio;
 	unsigned int			rt_priority;
+	int				latency_nice;
 
 	const struct sched_class	*sched_class;
 	struct sched_entity		se;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 878910e8b299..26b9758075e4 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -101,6 +101,24 @@ extern long calc_load_fold_active(struct rq *this_rq, long adjust);
  */
 #define NS_TO_JIFFIES(TIME)	((unsigned long)(TIME) / (NSEC_PER_SEC / HZ))
 
+/*
+ * 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
+
 /*
  * Increase resolution of nice-level calculations for 64-bit architectures.
  * The extra resolution improves shares distribution and load balancing of
-- 
2.17.2


  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 ` Parth Shah [this message]
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 ` [PATCH v4 3/4] sched: Allow sched_{get,set}attr to change latency_nice of the task Parth Shah
2020-02-25  6:54   ` 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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