From: Peter Zijlstra <pzijlstr@redhat.com>
Date: Sun, 3 Feb 2008 19:23:45 +0100
Subject: [sched] change the interactive interface
Message-id: 20080203183340.124870658@chello.nl
O-Subject: [RHEL5.2 PATCH 1/2] sched: change the interactive interface
Bugzilla: 250589

Change the /proc/sys/kernel/sched_fair interface that disables the
interactivity estimator that is new in 5.2 to
/proc/sys/kernel/sched_interactive because the customers insist on having
a weak interactivity form.

The new interface takes the values:
2 - strong (default, as previous RHEL-5 releases)
1 - weak; avoid starvation of tasks due to the interactivity bonus
0 - disabled; no interactivity bonus

For now, '1' is not implemented, but change the interface before 5.2 hits the
streets, otherwise we need to change it for 5.3 and the two versions will have
different interfaces.

Signed-off-by: Peter Zijlstra <pzijlstr@redhat.com>

Acked-by: Ingo Molnar <mingo@redhat.com>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 806ff8b..4bf2f47 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -118,7 +118,9 @@ extern unsigned long avenrun[];		/* Load averages */
 	load += n*(FIXED_1-exp); \
 	load >>= FSHIFT;
 
-extern unsigned int sched_fair;
+extern int sched_interactive;
+extern int sched_interactive_min;
+extern int sched_interactive_max;
 extern unsigned long total_forks;
 extern int nr_threads;
 extern int last_pid;
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index ac29a86..5faf2cd 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -155,7 +155,7 @@ enum
 	KERN_MAX_LOCK_DEPTH=74,
 	KERN_KDUMP_ON_INIT=75,	/* int: ia64 kdump with INIT */
  	KERN_PANIC_ON_NMI=76, /* int: whether we will panic on an unrecovered */
-	KERN_SCHED_FAIR=77,     /* int: disable the interactivity estimator */
+	KERN_SCHED_INTERACTIVE=77, /* int: disable the interactivity estimator */
 	KERN_LOCK_STAT=78,	/* int: enable lock statistics */
 	KERN_PROVE_LOCKING=79,	/* int: enable lock dependancy validation */
 	KERN_SOFTLOCKUP_THRESH=80, /* int: min time to report softlockups */
diff --git a/kernel/sched.c b/kernel/sched.c
index 0d71173..9452d75 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -867,7 +867,7 @@ static int recalc_task_prio(struct task_struct *p, unsigned long long now)
 	/* Caller must always ensure 'now >= p->timestamp' */
 	unsigned long sleep_time = now - p->timestamp;
 
-	if (batch_task(p) || sched_fair)
+	if (batch_task(p) || sched_interactive == 0)
 		sleep_time = 0;
 
 	if (likely(sleep_time > 0)) {
@@ -4064,7 +4064,15 @@ static inline struct task_struct *find_process_by_pid(pid_t pid)
 	return pid ? find_task_by_pid(pid) : current;
 }
 
-unsigned int sched_fair;
+/*
+ * interactive mode:
+ * 2 - strong (default)
+ * 1 - weak - avoids starvation of tasks due to interactive bonus
+ * 0 - disabled - no bonus at all
+ */
+int __read_mostly sched_interactive = 2;
+int sched_interactive_min = 0;
+int sched_interactive_max = 2;
 
 /* Actually do priority change: must hold rq lock. */
 static void __setscheduler(struct task_struct *p, int policy, int prio)
@@ -4081,7 +4089,7 @@ static void __setscheduler(struct task_struct *p, int policy, int prio)
 	 */
 	if (policy == SCHED_BATCH)
 		p->sleep_avg = 0;
-	if (policy == SCHED_NORMAL && sched_fair)
+	if (policy == SCHED_NORMAL && sched_interactive == 0)
 		p->sleep_avg = 0;
 	set_load_weight(p);
 }
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index e935b76..472cc83 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -272,12 +272,14 @@ static ctl_table root_table[] = {
 
 static ctl_table kern_table[] = {
 	{
-		.ctl_name	= KERN_SCHED_FAIR,
-		.procname	= "sched_fair",
-		.data		= &sched_fair,
+		.ctl_name	= KERN_SCHED_INTERACTIVE,
+		.procname	= "sched_interactive",
+		.data		= &sched_interactive,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= &proc_dointvec,
+		.proc_handler	= &proc_dointvec_minmax,
+		.extra1		= &sched_interactive_min,
+		.extra2		= &sched_interactive_max,
 	},
 	{
 		.ctl_name	= KERN_OSTYPE,