[Devel] [PATCH 6/9] Handle dont care groups

[Srivatsa Vaddagiri]

Deal with task-groups whose bandwidth hasnt been explicitly set by the
administrator. Unallocated CPU bandwidth is equally distributed among such
"don't care" groups.

Signed-off-by : Srivatsa Vaddagiri <vatsa at in.ibm.com>


 linux-2.6.18-root/include/linux/sched.h |    2 

---

 1 file changed, 91 insertions(+), 5 deletions(-)


---


diff -puN kernel/sched.c~dont_care kernel/sched.c
--- linux-2.6.20/kernel/sched.c~dont_care	2007-04-12 09:09:48.000000000 +0530
+++ linux-2.6.20-vatsa/kernel/sched.c	2007-04-12 11:07:15.000000000 +0530
@@ -227,6 +227,12 @@ static DEFINE_PER_CPU(struct task_grp_rq
 /* task-group object - maintains information about each task-group */
 struct task_grp {
 	unsigned short ticks, long_ticks; /* bandwidth given to task-group */
+ 	int left_over_pct;
+ 	int total_dont_care_grps;
+ 	int dont_care;          /* Does this group care for its bandwidth ? */
+ 	struct task_grp *parent;
+ 	struct list_head dont_care_list;
+ 	struct list_head list;
 	struct task_grp_rq *rq[NR_CPUS]; /* runqueue pointer for every cpu */
 };
 
@@ -7210,6 +7216,12 @@ void __init sched_init(void)
 
 	init_task_grp.ticks = CPU_CONTROL_SHORT_WINDOW;   /* 100% bandwidth */
 	init_task_grp.long_ticks = NUM_LONG_TICKS;
+ 	init_task_grp.left_over_pct = 100;  /* 100% unallocated bandwidth */
+ 	init_task_grp.parent = NULL;
+ 	init_task_grp.total_dont_care_grps = 1;	/* init_task_grp itself */
+ 	init_task_grp.dont_care = 1;
+ 	INIT_LIST_HEAD(&init_task_grp.dont_care_list);
+	list_add_tail(&init_task_grp.list, &init_task_grp.dont_care_list);
 
 	for_each_possible_cpu(i) {
 		struct rq *rq;
@@ -7382,19 +7394,50 @@ void set_curr_task(int cpu, struct task_
 
 #ifdef CONFIG_CPUMETER
 
+/* Distribute left over bandwidth equally to all "dont care" task groups */
+static void recalc_dontcare(struct task_grp *tg_root)
+{
+	int ticks;
+	struct list_head *entry;
+
+	if (!tg_root->total_dont_care_grps)
+		return;
+
+	ticks = ((tg_root->left_over_pct / tg_root->total_dont_care_grps) *
+		       				CPU_CONTROL_SHORT_WINDOW) / 100;
+
+	list_for_each(entry, &tg_root->dont_care_list) {
+		struct task_grp *tg;
+		int i;
+
+		tg = list_entry(entry, struct task_grp, list);
+		tg->ticks = ticks;
+		for_each_possible_cpu(i)
+			tg->rq[i]->ticks = tg->ticks;
+	}
+}
+
 /* Allocate runqueue structures for the new task-group */
-static int sched_create_group(void)
+static int sched_create_group(struct task_grp *tg_parent)
 {
 	struct task_grp *tg;
 	struct task_grp_rq *tgrq;
 	int i;
 
+	if (tg_parent->parent)
+		/* We don't support hierarchical CPU res mgmt (yet) */
+		return -EINVAL;
+
 	tg = kzalloc(sizeof(*tg), GFP_KERNEL);
 	if (!tg)
 		return -ENOMEM;
 
 	tg->ticks = CPU_CONTROL_SHORT_WINDOW;
 	tg->long_ticks = NUM_LONG_TICKS;
+	tg->parent = tg_parent;
+	tg->dont_care = 1;
+	tg->left_over_pct = 100;
+	INIT_LIST_HEAD(&tg->dont_care_list);
 
 	for_each_possible_cpu(i) {
 		tgrq = kzalloc(sizeof(*tgrq), GFP_KERNEL);
@@ -7404,6 +7447,15 @@ static int sched_create_group(void)
 		task_grp_rq_init(tgrq, tg);
 	}
 
+	if (tg->parent) {
+		tg->parent->total_dont_care_grps++;
+		list_add_tail(&tg->list, &tg->parent->dont_care_list);
+		recalc_dontcare(tg->parent);
+	} else {
+		tg->total_dont_care_grps = 1;
+		list_add_tail(&tg->list, &tg->dont_care_list);
+	}
+
 	/* A later patch will make 'tg' accessible beyond this function */
 	return 0;
 oom:
@@ -7418,6 +7470,16 @@ oom:
 static void sched_destroy_group(struct task_grp *tg)
 {
 	int i;
+	struct task_grp *tg_root = tg->parent;
+
+	if (!tg_root)
+		tg_root = tg;
+
+	if (tg->dont_care) {
+		tg_root->total_dont_care_grps--;
+		list_del(&tg->list);
+		recalc_dontcare(tg_root);
+	}
 
 	for_each_possible_cpu(i)
 		kfree(tg->rq[i]);
@@ -7428,12 +7490,33 @@ static void sched_destroy_group(struct t
 /* Assign quota to this group */
 static int sched_set_quota(struct task_grp *tg, int quota)
 {
-	int i;
+	int i, old_quota = 0;
+	struct task_grp *tg_root = tg->parent;
+
+	if (!tg_root)
+		tg_root = tg;
+
+	if (!tg->dont_care)
+		old_quota = (tg->ticks * 100) / CPU_CONTROL_SHORT_WINDOW;
+
+	if ((quota - old_quota) > tg_root->left_over_pct)
+		return -EINVAL;
+
+	if (tg->dont_care) {
+		tg->dont_care = 0;
+		tg_root->total_dont_care_grps--;
+		list_del(&tg->list);
+	}
 
 	tg->ticks = (quota * CPU_CONTROL_SHORT_WINDOW) / 100;
+	for_each_possible_cpu(i) {
+  		tg->rq[i]->ticks = tg->ticks;
+		tg->rq[i]->long_ticks = tg->long_ticks;
+	}
 
-	for_each_possible_cpu(i)
-		tg->rq[i]->ticks = tg->ticks;
+	/* xxx: needs some locking */
+	tg_root->left_over_pct -= (quota - old_quota);
+	recalc_dontcare(tg_root);
 
 	return 0;
 }
@@ -7446,7 +7529,10 @@ static inline int cpu_quota(struct task_
 /* Return assigned quota for this group */
 static int sched_get_quota(struct task_grp *tg)
 {
-	return cpu_quota(tg);
+	if (tg->dont_care)
+		return 0;
+	else
+		return cpu_quota(tg);
 }
 
 /*
_
-- 
Regards,
vatsa
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