From: Parth Shah <parth@linux.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: peterz@infradead.org, mingo@redhat.com,
vincent.guittot@linaro.org, patrick.bellasi@matbug.net,
valentin.schneider@arm.com, qais.yousef@arm.com, pavel@ucw.cz,
dhaval.giani@oracle.com, qperret@qperret.net,
David.Laight@ACULAB.COM, pjt@google.com, tj@kernel.org,
dietmar.eggemann@arm.com
Subject: [PATCH v2 1/3] sched: Introduce latency-tolerance as a per-task attribute
Date: Sun, 8 Dec 2019 11:34:08 +0530 [thread overview]
Message-ID: <20191208060410.17814-2-parth@linux.ibm.com> (raw)
In-Reply-To: <20191208060410.17814-1-parth@linux.ibm.com>
Latency-tolerance 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_tolerance = -20 indicates the task to have the least latency as
compared to the tasks having latency_tolerance = +19.
The latency_tolerance 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 84b26d38c929..d5f907d7a91a 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_tolerance;
const struct sched_class *sched_class;
struct sched_entity se;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 280a3c735935..3d68aaad02cc 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 tolerance is meant to provide scheduler hints about the relative
+ * latency requirements of a task with respect to other tasks.
+ * Thus a task with latency_tolerance == 19 can be hinted as the task with no
+ * latency requirements, in contrast to the task with latency_tolerance == -20
+ * which should be given priority in terms of lower latency.
+ */
+#define MAX_LATENCY_TOLERANCE 19
+#define MIN_LATENCY_TOLERANCE -20
+
+#define LATENCY_TOLERANCE_WIDTH \
+ (MAX_LATENCY_TOLERANCE - MIN_LATENCY_TOLERANCE + 1)
+
+/*
+ * Default tasks should be treated as a task with latency_tolerance = 0.
+ */
+#define DEFAULT_LATENCY_TOLERANCE 0
+
/*
* Increase resolution of nice-level calculations for 64-bit architectures.
* The extra resolution improves shares distribution and load balancing of
--
2.17.2
next prev parent reply other threads:[~2019-12-08 6:04 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-08 6:04 [PATCH v2 0/3] Introduce per-task latency_tolerance for scheduler hints Parth Shah
2019-12-08 6:04 ` Parth Shah [this message]
2019-12-08 6:04 ` [PATCH v2 2/3] sched/core: Propagate parent task's latency requirements to the child task Parth Shah
2019-12-08 6:04 ` [PATCH v2 3/3] sched: Allow sched_{get,set}attr to change latency_tolerance of the task Parth Shah
2020-01-15 20:33 ` [PATCH v2 0/3] Introduce per-task latency_tolerance for scheduler hints Dhaval Giani
2020-01-16 12:04 ` Parth Shah
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