revert ("sched: fair-group: SMP-nice for group scheduling")
Yanmin Zhang reported:
Comparing with 2.6.25, volanoMark has big regression with kernel 2.6.26-rc1.
It's about 50% on my 8-core stoakley, 16-core tigerton, and Itanium Montecito.
With bisect, I located the following patch:
| 18d95a2832c1392a2d63227a7a6d433cb9f2037e is first bad commit
| commit 18d95a2832c1392a2d63227a7a6d433cb9f2037e
| Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
| Date: Sat Apr 19 19:45:00 2008 +0200
|
| sched: fair-group: SMP-nice for group scheduling
Revert it so that we get v2.6.25 behavior.
Bisected-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched.c b/kernel/sched.c
index 3dc13f0..bfb8ad8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -398,43 +398,6 @@
*/
struct list_head leaf_cfs_rq_list;
struct task_group *tg; /* group that "owns" this runqueue */
-
-#ifdef CONFIG_SMP
- unsigned long task_weight;
- unsigned long shares;
- /*
- * We need space to build a sched_domain wide view of the full task
- * group tree, in order to avoid depending on dynamic memory allocation
- * during the load balancing we place this in the per cpu task group
- * hierarchy. This limits the load balancing to one instance per cpu,
- * but more should not be needed anyway.
- */
- struct aggregate_struct {
- /*
- * load = weight(cpus) * f(tg)
- *
- * Where f(tg) is the recursive weight fraction assigned to
- * this group.
- */
- unsigned long load;
-
- /*
- * part of the group weight distributed to this span.
- */
- unsigned long shares;
-
- /*
- * The sum of all runqueue weights within this span.
- */
- unsigned long rq_weight;
-
- /*
- * Weight contributed by tasks; this is the part we can
- * influence by moving tasks around.
- */
- unsigned long task_weight;
- } aggregate;
-#endif
#endif
};
@@ -1508,326 +1471,6 @@
static unsigned long target_load(int cpu, int type);
static unsigned long cpu_avg_load_per_task(int cpu);
static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
-
-#ifdef CONFIG_FAIR_GROUP_SCHED
-
-/*
- * Group load balancing.
- *
- * We calculate a few balance domain wide aggregate numbers; load and weight.
- * Given the pictures below, and assuming each item has equal weight:
- *
- * root 1 - thread
- * / | \ A - group
- * A 1 B
- * /|\ / \
- * C 2 D 3 4
- * | |
- * 5 6
- *
- * load:
- * A and B get 1/3-rd of the total load. C and D get 1/3-rd of A's 1/3-rd,
- * which equals 1/9-th of the total load.
- *
- * shares:
- * The weight of this group on the selected cpus.
- *
- * rq_weight:
- * Direct sum of all the cpu's their rq weight, e.g. A would get 3 while
- * B would get 2.
- *
- * task_weight:
- * Part of the rq_weight contributed by tasks; all groups except B would
- * get 1, B gets 2.
- */
-
-static inline struct aggregate_struct *
-aggregate(struct task_group *tg, struct sched_domain *sd)
-{
- return &tg->cfs_rq[sd->first_cpu]->aggregate;
-}
-
-typedef void (*aggregate_func)(struct task_group *, struct sched_domain *);
-
-/*
- * Iterate the full tree, calling @down when first entering a node and @up when
- * leaving it for the final time.
- */
-static
-void aggregate_walk_tree(aggregate_func down, aggregate_func up,
- struct sched_domain *sd)
-{
- struct task_group *parent, *child;
-
- rcu_read_lock();
- parent = &root_task_group;
-down:
- (*down)(parent, sd);
- list_for_each_entry_rcu(child, &parent->children, siblings) {
- parent = child;
- goto down;
-
-up:
- continue;
- }
- (*up)(parent, sd);
-
- child = parent;
- parent = parent->parent;
- if (parent)
- goto up;
- rcu_read_unlock();
-}
-
-/*
- * Calculate the aggregate runqueue weight.
- */
-static
-void aggregate_group_weight(struct task_group *tg, struct sched_domain *sd)
-{
- unsigned long rq_weight = 0;
- unsigned long task_weight = 0;
- int i;
-
- for_each_cpu_mask(i, sd->span) {
- rq_weight += tg->cfs_rq[i]->load.weight;
- task_weight += tg->cfs_rq[i]->task_weight;
- }
-
- aggregate(tg, sd)->rq_weight = rq_weight;
- aggregate(tg, sd)->task_weight = task_weight;
-}
-
-/*
- * Compute the weight of this group on the given cpus.
- */
-static
-void aggregate_group_shares(struct task_group *tg, struct sched_domain *sd)
-{
- unsigned long shares = 0;
- int i;
-
- for_each_cpu_mask(i, sd->span)
- shares += tg->cfs_rq[i]->shares;
-
- if ((!shares && aggregate(tg, sd)->rq_weight) || shares > tg->shares)
- shares = tg->shares;
-
- aggregate(tg, sd)->shares = shares;
-}
-
-/*
- * Compute the load fraction assigned to this group, relies on the aggregate
- * weight and this group's parent's load, i.e. top-down.
- */
-static
-void aggregate_group_load(struct task_group *tg, struct sched_domain *sd)
-{
- unsigned long load;
-
- if (!tg->parent) {
- int i;
-
- load = 0;
- for_each_cpu_mask(i, sd->span)
- load += cpu_rq(i)->load.weight;
-
- } else {
- load = aggregate(tg->parent, sd)->load;
-
- /*
- * shares is our weight in the parent's rq so
- * shares/parent->rq_weight gives our fraction of the load
- */
- load *= aggregate(tg, sd)->shares;
- load /= aggregate(tg->parent, sd)->rq_weight + 1;
- }
-
- aggregate(tg, sd)->load = load;
-}
-
-static void __set_se_shares(struct sched_entity *se, unsigned long shares);
-
-/*
- * Calculate and set the cpu's group shares.
- */
-static void
-__update_group_shares_cpu(struct task_group *tg, struct sched_domain *sd,
- int tcpu)
-{
- int boost = 0;
- unsigned long shares;
- unsigned long rq_weight;
-
- if (!tg->se[tcpu])
- return;
-
- rq_weight = tg->cfs_rq[tcpu]->load.weight;
-
- /*
- * If there are currently no tasks on the cpu pretend there is one of
- * average load so that when a new task gets to run here it will not
- * get delayed by group starvation.
- */
- if (!rq_weight) {
- boost = 1;
- rq_weight = NICE_0_LOAD;
- }
-
- /*
- * \Sum shares * rq_weight
- * shares = -----------------------
- * \Sum rq_weight
- *
- */
- shares = aggregate(tg, sd)->shares * rq_weight;
- shares /= aggregate(tg, sd)->rq_weight + 1;
-
- /*
- * record the actual number of shares, not the boosted amount.
- */
- tg->cfs_rq[tcpu]->shares = boost ? 0 : shares;
-
- if (shares < MIN_SHARES)
- shares = MIN_SHARES;
- else if (shares > MAX_SHARES)
- shares = MAX_SHARES;
-
- __set_se_shares(tg->se[tcpu], shares);
-}
-
-/*
- * Re-adjust the weights on the cpu the task came from and on the cpu the
- * task went to.
- */
-static void
-__move_group_shares(struct task_group *tg, struct sched_domain *sd,
- int scpu, int dcpu)
-{
- unsigned long shares;
-
- shares = tg->cfs_rq[scpu]->shares + tg->cfs_rq[dcpu]->shares;
-
- __update_group_shares_cpu(tg, sd, scpu);
- __update_group_shares_cpu(tg, sd, dcpu);
-
- /*
- * ensure we never loose shares due to rounding errors in the
- * above redistribution.
- */
- shares -= tg->cfs_rq[scpu]->shares + tg->cfs_rq[dcpu]->shares;
- if (shares)
- tg->cfs_rq[dcpu]->shares += shares;
-}
-
-/*
- * Because changing a group's shares changes the weight of the super-group
- * we need to walk up the tree and change all shares until we hit the root.
- */
-static void
-move_group_shares(struct task_group *tg, struct sched_domain *sd,
- int scpu, int dcpu)
-{
- while (tg) {
- __move_group_shares(tg, sd, scpu, dcpu);
- tg = tg->parent;
- }
-}
-
-static
-void aggregate_group_set_shares(struct task_group *tg, struct sched_domain *sd)
-{
- unsigned long shares = aggregate(tg, sd)->shares;
- int i;
-
- for_each_cpu_mask(i, sd->span) {
- struct rq *rq = cpu_rq(i);
- unsigned long flags;
-
- spin_lock_irqsave(&rq->lock, flags);
- __update_group_shares_cpu(tg, sd, i);
- spin_unlock_irqrestore(&rq->lock, flags);
- }
-
- aggregate_group_shares(tg, sd);
-
- /*
- * ensure we never loose shares due to rounding errors in the
- * above redistribution.
- */
- shares -= aggregate(tg, sd)->shares;
- if (shares) {
- tg->cfs_rq[sd->first_cpu]->shares += shares;
- aggregate(tg, sd)->shares += shares;
- }
-}
-
-/*
- * Calculate the accumulative weight and recursive load of each task group
- * while walking down the tree.
- */
-static
-void aggregate_get_down(struct task_group *tg, struct sched_domain *sd)
-{
- aggregate_group_weight(tg, sd);
- aggregate_group_shares(tg, sd);
- aggregate_group_load(tg, sd);
-}
-
-/*
- * Rebalance the cpu shares while walking back up the tree.
- */
-static
-void aggregate_get_up(struct task_group *tg, struct sched_domain *sd)
-{
- aggregate_group_set_shares(tg, sd);
-}
-
-static DEFINE_PER_CPU(spinlock_t, aggregate_lock);
-
-static void __init init_aggregate(void)
-{
- int i;
-
- for_each_possible_cpu(i)
- spin_lock_init(&per_cpu(aggregate_lock, i));
-}
-
-static int get_aggregate(struct sched_domain *sd)
-{
- if (!spin_trylock(&per_cpu(aggregate_lock, sd->first_cpu)))
- return 0;
-
- aggregate_walk_tree(aggregate_get_down, aggregate_get_up, sd);
- return 1;
-}
-
-static void put_aggregate(struct sched_domain *sd)
-{
- spin_unlock(&per_cpu(aggregate_lock, sd->first_cpu));
-}
-
-static void cfs_rq_set_shares(struct cfs_rq *cfs_rq, unsigned long shares)
-{
- cfs_rq->shares = shares;
-}
-
-#else
-
-static inline void init_aggregate(void)
-{
-}
-
-static inline int get_aggregate(struct sched_domain *sd)
-{
- return 0;
-}
-
-static inline void put_aggregate(struct sched_domain *sd)
-{
-}
-#endif
-
#else /* CONFIG_SMP */
#ifdef CONFIG_FAIR_GROUP_SCHED
@@ -1848,14 +1491,26 @@
#define sched_class_highest (&rt_sched_class)
-static void inc_nr_running(struct rq *rq)
+static inline void inc_load(struct rq *rq, const struct task_struct *p)
{
- rq->nr_running++;
+ update_load_add(&rq->load, p->se.load.weight);
}
-static void dec_nr_running(struct rq *rq)
+static inline void dec_load(struct rq *rq, const struct task_struct *p)
+{
+ update_load_sub(&rq->load, p->se.load.weight);
+}
+
+static void inc_nr_running(struct task_struct *p, struct rq *rq)
+{
+ rq->nr_running++;
+ inc_load(rq, p);
+}
+
+static void dec_nr_running(struct task_struct *p, struct rq *rq)
{
rq->nr_running--;
+ dec_load(rq, p);
}
static void set_load_weight(struct task_struct *p)
@@ -1947,7 +1602,7 @@
rq->nr_uninterruptible--;
enqueue_task(rq, p, wakeup);
- inc_nr_running(rq);
+ inc_nr_running(p, rq);
}
/*
@@ -1959,7 +1614,7 @@
rq->nr_uninterruptible++;
dequeue_task(rq, p, sleep);
- dec_nr_running(rq);
+ dec_nr_running(p, rq);
}
/**
@@ -2612,7 +2267,7 @@
* management (if any):
*/
p->sched_class->task_new(rq, p);
- inc_nr_running(rq);
+ inc_nr_running(p, rq);
}
check_preempt_curr(rq, p);
#ifdef CONFIG_SMP
@@ -3603,12 +3258,9 @@
unsigned long imbalance;
struct rq *busiest;
unsigned long flags;
- int unlock_aggregate;
cpus_setall(*cpus);
- unlock_aggregate = get_aggregate(sd);
-
/*
* When power savings policy is enabled for the parent domain, idle
* sibling can pick up load irrespective of busy siblings. In this case,
@@ -3724,9 +3376,8 @@
if (!ld_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
- ld_moved = -1;
-
- goto out;
+ return -1;
+ return ld_moved;
out_balanced:
schedstat_inc(sd, lb_balanced[idle]);
@@ -3741,13 +3392,8 @@
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
- ld_moved = -1;
- else
- ld_moved = 0;
-out:
- if (unlock_aggregate)
- put_aggregate(sd);
- return ld_moved;
+ return -1;
+ return 0;
}
/*
@@ -4934,8 +4580,10 @@
goto out_unlock;
}
on_rq = p->se.on_rq;
- if (on_rq)
+ if (on_rq) {
dequeue_task(rq, p, 0);
+ dec_load(rq, p);
+ }
p->static_prio = NICE_TO_PRIO(nice);
set_load_weight(p);
@@ -4945,6 +4593,7 @@
if (on_rq) {
enqueue_task(rq, p, 0);
+ inc_load(rq, p);
/*
* If the task increased its priority or is running and
* lowered its priority, then reschedule its CPU:
@@ -7319,7 +6968,6 @@
SD_INIT(sd, ALLNODES);
set_domain_attribute(sd, attr);
sd->span = *cpu_map;
- sd->first_cpu = first_cpu(sd->span);
cpu_to_allnodes_group(i, cpu_map, &sd->groups, tmpmask);
p = sd;
sd_allnodes = 1;
@@ -7330,7 +6978,6 @@
SD_INIT(sd, NODE);
set_domain_attribute(sd, attr);
sched_domain_node_span(cpu_to_node(i), &sd->span);
- sd->first_cpu = first_cpu(sd->span);
sd->parent = p;
if (p)
p->child = sd;
@@ -7342,7 +6989,6 @@
SD_INIT(sd, CPU);
set_domain_attribute(sd, attr);
sd->span = *nodemask;
- sd->first_cpu = first_cpu(sd->span);
sd->parent = p;
if (p)
p->child = sd;
@@ -7354,7 +7000,6 @@
SD_INIT(sd, MC);
set_domain_attribute(sd, attr);
sd->span = cpu_coregroup_map(i);
- sd->first_cpu = first_cpu(sd->span);
cpus_and(sd->span, sd->span, *cpu_map);
sd->parent = p;
p->child = sd;
@@ -7367,7 +7012,6 @@
SD_INIT(sd, SIBLING);
set_domain_attribute(sd, attr);
sd->span = per_cpu(cpu_sibling_map, i);
- sd->first_cpu = first_cpu(sd->span);
cpus_and(sd->span, sd->span, *cpu_map);
sd->parent = p;
p->child = sd;
@@ -8037,7 +7681,6 @@
}
#ifdef CONFIG_SMP
- init_aggregate();
init_defrootdomain();
#endif
@@ -8602,11 +8245,14 @@
#endif
#ifdef CONFIG_FAIR_GROUP_SCHED
-static void __set_se_shares(struct sched_entity *se, unsigned long shares)
+static void set_se_shares(struct sched_entity *se, unsigned long shares)
{
struct cfs_rq *cfs_rq = se->cfs_rq;
+ struct rq *rq = cfs_rq->rq;
int on_rq;
+ spin_lock_irq(&rq->lock);
+
on_rq = se->on_rq;
if (on_rq)
dequeue_entity(cfs_rq, se, 0);
@@ -8616,17 +8262,8 @@
if (on_rq)
enqueue_entity(cfs_rq, se, 0);
-}
-static void set_se_shares(struct sched_entity *se, unsigned long shares)
-{
- struct cfs_rq *cfs_rq = se->cfs_rq;
- struct rq *rq = cfs_rq->rq;
- unsigned long flags;
-
- spin_lock_irqsave(&rq->lock, flags);
- __set_se_shares(se, shares);
- spin_unlock_irqrestore(&rq->lock, flags);
+ spin_unlock_irq(&rq->lock);
}
static DEFINE_MUTEX(shares_mutex);
@@ -8665,13 +8302,8 @@
* w/o tripping rebalance_share or load_balance_fair.
*/
tg->shares = shares;
- for_each_possible_cpu(i) {
- /*
- * force a rebalance
- */
- cfs_rq_set_shares(tg->cfs_rq[i], 0);
+ for_each_possible_cpu(i)
set_se_shares(tg->se[i], shares);
- }
/*
* Enable load balance activity on this group, by inserting it back on