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Date: Tue, 1 Jun 2010 09:12:41 GMT
From: tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
a.p.zijlstra@...llo.nl, efault@....de, tglx@...utronix.de,
mingo@...e.hu
Subject: [tip:sched/urgent] sched: Fix wake_affine() vs RT tasks
Commit-ID: e51fd5e22e12b39f49b1bb60b37b300b17378a43
Gitweb: http://git.kernel.org/tip/e51fd5e22e12b39f49b1bb60b37b300b17378a43
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Mon, 31 May 2010 12:37:30 +0200
Committer: Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 1 Jun 2010 09:27:16 +0200
sched: Fix wake_affine() vs RT tasks
Mike reports that since e9e9250b (sched: Scale down cpu_power due to RT
tasks), wake_affine() goes funny on RT tasks due to them still having a
!0 weight and wake_affine() still subtracts that from the rq weight.
Since nobody should be using se->weight for RT tasks, set the value to
zero. Also, since we now use ->cpu_power to normalize rq weights to
account for RT cpu usage, add that factor into the imbalance computation.
Reported-by: Mike Galbraith <efault@....de>
Tested-by: Mike Galbraith <efault@....de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <1275316109.27810.22969.camel@...ns>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
kernel/sched.c | 24 ++++++------------------
kernel/sched_fair.c | 22 ++++++++++++++++------
2 files changed, 22 insertions(+), 24 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index d484081..f8b8996 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -544,6 +544,8 @@ struct rq {
struct root_domain *rd;
struct sched_domain *sd;
+ unsigned long cpu_power;
+
unsigned char idle_at_tick;
/* For active balancing */
int post_schedule;
@@ -1499,24 +1501,9 @@ static unsigned long target_load(int cpu, int type)
return max(rq->cpu_load[type-1], total);
}
-static struct sched_group *group_of(int cpu)
-{
- struct sched_domain *sd = rcu_dereference_sched(cpu_rq(cpu)->sd);
-
- if (!sd)
- return NULL;
-
- return sd->groups;
-}
-
static unsigned long power_of(int cpu)
{
- struct sched_group *group = group_of(cpu);
-
- if (!group)
- return SCHED_LOAD_SCALE;
-
- return group->cpu_power;
+ return cpu_rq(cpu)->cpu_power;
}
static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
@@ -1854,8 +1841,8 @@ static void dec_nr_running(struct rq *rq)
static void set_load_weight(struct task_struct *p)
{
if (task_has_rt_policy(p)) {
- p->se.load.weight = prio_to_weight[0] * 2;
- p->se.load.inv_weight = prio_to_wmult[0] >> 1;
+ p->se.load.weight = 0;
+ p->se.load.inv_weight = WMULT_CONST;
return;
}
@@ -7605,6 +7592,7 @@ void __init sched_init(void)
#ifdef CONFIG_SMP
rq->sd = NULL;
rq->rd = NULL;
+ rq->cpu_power = SCHED_LOAD_SCALE;
rq->post_schedule = 0;
rq->active_balance = 0;
rq->next_balance = jiffies;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 217e4a9..eed35ed 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1225,7 +1225,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
unsigned long this_load, load;
int idx, this_cpu, prev_cpu;
unsigned long tl_per_task;
- unsigned int imbalance;
struct task_group *tg;
unsigned long weight;
int balanced;
@@ -1252,8 +1251,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
tg = task_group(p);
weight = p->se.load.weight;
- imbalance = 100 + (sd->imbalance_pct - 100) / 2;
-
/*
* In low-load situations, where prev_cpu is idle and this_cpu is idle
* due to the sync cause above having dropped this_load to 0, we'll
@@ -1263,9 +1260,21 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
* Otherwise check if either cpus are near enough in load to allow this
* task to be woken on this_cpu.
*/
- balanced = !this_load ||
- 100*(this_load + effective_load(tg, this_cpu, weight, weight)) <=
- imbalance*(load + effective_load(tg, prev_cpu, 0, weight));
+ if (this_load) {
+ unsigned long this_eff_load, prev_eff_load;
+
+ this_eff_load = 100;
+ this_eff_load *= power_of(prev_cpu);
+ this_eff_load *= this_load +
+ effective_load(tg, this_cpu, weight, weight);
+
+ prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
+ prev_eff_load *= power_of(this_cpu);
+ prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
+
+ balanced = this_eff_load <= prev_eff_load;
+ } else
+ balanced = true;
/*
* If the currently running task will sleep within
@@ -2298,6 +2307,7 @@ static void update_cpu_power(struct sched_domain *sd, int cpu)
if (!power)
power = 1;
+ cpu_rq(cpu)->cpu_power = power;
sdg->cpu_power = power;
}
--
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