Merge "sched: Improve the scheduler"

fs/proc/base.c

@@ -1654,6 +1654,58 @@ static const struct file_operations proc_pid_sched_group_id_operations = {
 	.release	= single_release,
 };
 
+static int sched_low_latency_show(struct seq_file *m, void *v)
+{
+	struct inode *inode = m->private;
+	struct task_struct *p;
+	bool low_latency;
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+
+	low_latency = p->low_latency;
+	seq_printf(m, "%d\n", low_latency);
+
+	put_task_struct(p);
+
+	return 0;
+}
+
+static ssize_t
+sched_low_latency_write(struct file *file, const char __user *buf,
+	    size_t count, loff_t *offset)
+{
+	struct task_struct *p = get_proc_task(file_inode(file));
+	bool low_latency;
+	int err;
+
+	if (!p)
+		return -ESRCH;
+
+	err =  kstrtobool_from_user(buf, count, &low_latency);
+	if (err)
+		goto out;
+
+	p->low_latency = low_latency;
+out:
+	put_task_struct(p);
+	return err < 0 ? err : count;
+}
+
+static int sched_low_latency_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, sched_low_latency_show, inode);
+}
+
+static const struct file_operations proc_pid_sched_low_latency_operations = {
+	.open		= sched_low_latency_open,
+	.read		= seq_read,
+	.write		= sched_low_latency_write,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
 #endif	/* CONFIG_SCHED_WALT */
 
 #ifdef CONFIG_SCHED_AUTOGROUP
@@ -3326,6 +3378,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 	REG("sched_group_id", 00666, proc_pid_sched_group_id_operations),
 	REG("sched_boost", 0666,  proc_task_boost_enabled_operations),
 	REG("sched_boost_period_ms", 0666, proc_task_boost_period_operations),
+	REG("sched_low_latency", 00666, proc_pid_sched_low_latency_operations),
 #endif
 #ifdef CONFIG_SCHED_DEBUG
 	REG("sched",      S_IRUGO|S_IWUSR, proc_pid_sched_operations),

include/linux/sched.h

@@ -877,6 +877,7 @@ struct task_struct {
 	u64 cpu_cycles;
 	bool misfit;
 	u32 unfilter;
+	bool low_latency;
 #endif
 
 #ifdef CONFIG_CGROUP_SCHED

include/trace/events/sched.h

@@ -1243,6 +1243,7 @@ TRACE_EVENT(sched_task_util,
 		__field(int,		start_cpu)
 		__field(u32,		unfilter)
 		__field(unsigned long,  cpus_allowed)
+		__field(bool,		low_latency)
 	),
 
 	TP_fast_assign(
@@ -1263,19 +1264,21 @@ TRACE_EVENT(sched_task_util,
 		__entry->start_cpu		= start_cpu;
 #ifdef CONFIG_SCHED_WALT
 		__entry->unfilter		= p->unfilter;
+		__entry->low_latency		= p->low_latency;
 #else
 		__entry->unfilter		= 0;
+		__entry->low_latency		= 0;
 #endif
 		__entry->cpus_allowed           = cpumask_bits(&p->cpus_allowed)[0];
 	),
 
-	TP_printk("pid=%d comm=%s util=%lu prev_cpu=%d candidates=%#lx best_energy_cpu=%d sync=%d need_idle=%d fastpath=%d placement_boost=%d latency=%llu stune_boosted=%d is_rtg=%d rtg_skip_min=%d start_cpu=%d unfilter=%u affine=%#lx",
+	TP_printk("pid=%d comm=%s util=%lu prev_cpu=%d candidates=%#lx best_energy_cpu=%d sync=%d need_idle=%d fastpath=%d placement_boost=%d latency=%llu stune_boosted=%d is_rtg=%d rtg_skip_min=%d start_cpu=%d unfilter=%u affine=%#lx low_latency=%d`",
 		__entry->pid, __entry->comm, __entry->util, __entry->prev_cpu,
 		__entry->candidates, __entry->best_energy_cpu, __entry->sync,
 		__entry->need_idle, __entry->fastpath, __entry->placement_boost,
 		__entry->latency, __entry->stune_boosted,
 		__entry->is_rtg, __entry->rtg_skip_min, __entry->start_cpu,
-		__entry->unfilter, __entry->cpus_allowed)
+		__entry->unfilter, __entry->cpus_allowed, __entry->low_latency)
 );
 
 /*

kernel/sched/core.c

@@ -2857,6 +2857,9 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
 	p->boost			= 0;
 	p->boost_expires		= 0;
 	p->boost_period			= 0;
+#ifdef CONFIG_SCHED_WALT
+	p->low_latency			= 0;
+#endif
 	INIT_LIST_HEAD(&p->se.group_node);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED

kernel/sched/fair.c

@@ -4125,9 +4125,20 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 			thresh >>= 1;
 
 		vruntime -= thresh;
-		if (entity_is_task(se) && per_task_boost(task_of(se)) ==
+		if (entity_is_task(se)) {
+			if (per_task_boost(task_of(se)) ==
 						TASK_BOOST_STRICT_MAX)
 				vruntime -= sysctl_sched_latency;
+#ifdef CONFIG_SCHED_WALT
+			else if (unlikely(task_of(se)->low_latency)) {
+				vruntime -= sysctl_sched_latency;
+				vruntime -= thresh;
+				se->vruntime = min_vruntime(vruntime,
+							se->vruntime);
+				return;
+			}
+#endif
+		}
 	}
 
 	/* ensure we never gain time by being placed backwards. */