[PATCH 4/7] CPU controller V1 - Handle dont care groups

Srivatsa Vaddagiri
2006-08-20T17:45:51Z

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@in.ibm.com>

include/linux/sched.h | 2 -
kernel/sched.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 80 insertions(+), 4 deletions(-)

diff -puN kernel/sched.c~cpu_ctlr_handle_dont_cares kernel/sched.c
--- linux-2.6.18-rc3/kernel/sched.c~cpu_ctlr_handle_dont_cares 2006-08-20 21:58:30.000000000 +0530
+++ linux-2.6.18-rc3-root/kernel/sched.c 2006-08-20 21:59:19.000000000 +0530
@@ -229,6 +229,12 @@ static DEFINE_PER_CPU(struct task_grp_rq
/* task-group object - maintains information about each task-group */
struct task_grp {
int ticks; /* bandwidth given to the 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 */
};

@@ -6915,6 +6921,12 @@ void __init sched_init(void)
int i, j, k;

init_task_grp.ticks = -1; /* Unlimited bandwidth */
+ 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 prio_array *array;
@@ -7069,8 +7081,31 @@ 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) * 5 * HZ) / 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 */
-void *sched_alloc_group(void)
+void *sched_alloc_group(struct task_grp *tg_parent)
{
struct task_grp *tg;
struct task_grp_rq *tgrq;
@@ -7081,6 +7116,11 @@ void *sched_alloc_group(void)
return NULL;

tg->ticks = -1; /* No limit */
+ tg->parent = tg_parent;
+ tg->dont_care = 1;
+ tg->left_over_pct = 100;
+ tg->ticks = -1; /* No limit */
+ INIT_LIST_HEAD(&tg->dont_care_list);

for_each_possible_cpu(i) {
tgrq = kzalloc(sizeof(*tgrq), GFP_KERNEL);
@@ -7090,6 +7130,15 @@ void *sched_alloc_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);
+ }
+
return tg;
oom:
while (i--)
@@ -7103,6 +7152,16 @@ oom:
void sched_dealloc_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]);
@@ -7113,7 +7172,20 @@ void sched_dealloc_group(struct task_grp
/* Assign quota to this group */
void sched_assign_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) {
+ tg->dont_care = 0;
+ tg_root->total_dont_care_grps--;
+ list_del(&tg->list);
+ } else
+ old_quota = (tg->ticks * 100) / (5 * HZ);
+
+ tg_root->left_over_pct -= (quota - old_quota);

/* xxx: check validity of quota */
tg->ticks = (quota * 5 * HZ) / 100;
@@ -7121,6 +7193,7 @@ void sched_assign_quota(struct task_grp
for_each_possible_cpu(i)
tg->rq[i]->ticks = tg->ticks;

+ recalc_dontcare(tg_root);
}

static inline int cpu_quota(struct task_grp *tg)
@@ -7138,7 +7211,10 @@ static inline int cpu_quota(struct task_
/* Return assigned quota for this group */
int sched_get_quota(struct task_grp *tg)
{
- return cpu_quota(tg);
+ if (tg->dont_care)
+ return 0;
+ else
+ return cpu_quota(tg);
}

/*
diff -puN include/linux/sched.h~cpu_ctlr_handle_dont_cares include/linux/sched.h
--- linux-2.6.18-rc3/include/linux/sched.h~cpu_ctlr_handle_dont_cares 2006-08-20 21:58:30.000000000 +0530
+++ linux-2.6.18-rc3-root/include/linux/sched.h 2006-08-20 21:58:30.000000000 +0530
@@ -1608,7 +1608,7 @@ static inline int try_to_freeze(void) {
#ifdef CONFIG_CPUMETER
struct task_grp;
struct task_grp_ops {
- void *(*alloc_group)(void);
+ void *(*alloc_group)(struct task_grp *grp_parent);
void (*dealloc_group)(struct task_grp *grp);
void (*assign_quota)(struct task_grp *grp, int quota);
int (*pre_move_task)(struct task_struct *tsk, struct task_grp *old,

_
--
Regards,
vatsa