This is a note to let you know that I've just added the patch titled
sched: Fix wake_affine() vs RT tasks
to the 2.6.32-longterm tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/longterm/longterm-queue-2.6.32.git;a=summary
The filename of the patch is:
0028-sched-Fix-wake_affine-vs-RT-tasks.patch
and it can be found in the queue-2.6.32 subdirectory.
If you, or anyone else, feels it should not be added to the 2.6.32 longterm
tree,
please let <[email protected]> know about it.
>From 13c94b2cb85709e6f8cdf80595e6245aaa50aa83 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <[email protected]>
Date: Thu, 10 Feb 2011 10:23:29 +0100
Subject: sched: Fix wake_affine() vs RT tasks
Commit: e51fd5e22e12b39f49b1bb60b37b300b17378a43 upstream
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 <[email protected]>
Tested-by: Mike Galbraith <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
LKML-Reference: <1275316109.27810.22969.camel@twins>
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Mike Galbraith <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/sched.c | 25 +++++++------------------
kernel/sched_fair.c | 22 ++++++++++++++++------
2 files changed, 23 insertions(+), 24 deletions(-)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -533,6 +533,8 @@ 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;
@@ -1520,24 +1522,9 @@ static unsigned long target_load(int cpu
return max(rq->cpu_load[type-1], total);
}
-static struct sched_group *group_of(int cpu)
-{
- struct sched_domain *sd = rcu_dereference(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);
@@ -1932,8 +1919,8 @@ 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;
}
@@ -3833,6 +3820,7 @@ static void update_cpu_power(struct sche
if (!power)
power = 1;
+ cpu_rq(cpu)->cpu_power = power;
sdg->cpu_power = power;
}
@@ -9788,6 +9776,7 @@ 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;
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1222,7 +1222,6 @@ static int wake_affine(struct sched_doma
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;
@@ -1262,8 +1261,6 @@ static int wake_affine(struct sched_doma
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
@@ -1273,9 +1270,22 @@ static int wake_affine(struct sched_doma
* 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;
+
rcu_read_unlock();
/*
Patches currently in longterm-queue-2.6.32 which might be from
[email protected] are
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