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SubjectRe: [PATCH v5 5/7] sched: compute runnable load avg in cpu_load and cpu_avg_load_per_task
On 05/07/2013 02:34 AM, Paul Turner wrote:
>> > Current load balance doesn't consider slept task's load which is
>> > represented by blocked_load_avg. And the slept task is not on_rq, so
>> > consider it in load balance is a little strange.
> The load-balancer has a longer time horizon; think of blocked_loag_avg
> to be a signal for the load, already assigned to this cpu, which is
> expected to appear (within roughly the next quantum).
>
> Consider the following scenario:
>
> tasks: A,B (40% busy), C (90% busy)
>
> Suppose we have:
> CPU 0: CPU 1:
> A C
> B
>
> Then, when C blocks the load balancer ticks.
>
> If we considered only runnable_load then A or B would be eligible for
> migration to CPU 1, which is essentially where we are today.
>

here is the changed patch according to Paul's comments. Is that you liked, Paul? :)

---

From 1d7290530e2ee402874bbce39297bb1cfd882339 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@intel.com>
Date: Sat, 17 Nov 2012 13:56:11 +0800
Subject: [PATCH 5/7] sched: compute runnable load avg in cpu_load and
cpu_avg_load_per_task

They are the base values in load balance, update them with rq runnable
load average, then the load balance will consider runnable load avg
naturally.

Signed-off-by: Alex Shi <alex.shi@intel.com>
---
kernel/sched/core.c | 16 ++++++++++++++--
kernel/sched/fair.c | 8 ++++++--
2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 33d9a858..f4c6cac 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2536,9 +2536,14 @@ static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
void update_idle_cpu_load(struct rq *this_rq)
{
unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
- unsigned long load = this_rq->load.weight;
+ unsigned long load;
unsigned long pending_updates;

+#ifdef CONFIG_SMP
+ load = this_rq->cfs.runnable_load_avg + this_rq->cfs.blocked_load_avg;
+#else
+ load = this_rq->load.weight;
+#endif
/*
* bail if there's load or we're actually up-to-date.
*/
@@ -2582,11 +2587,18 @@ void update_cpu_load_nohz(void)
*/
static void update_cpu_load_active(struct rq *this_rq)
{
+ unsigned long load;
+
+#ifdef CONFIG_SMP
+ load = this_rq->cfs.runnable_load_avg + this_rq->cfs.blocked_load_avg;
+#else
+ load = this_rq->load.weight;
+#endif
/*
* See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
*/
this_rq->last_load_update_tick = jiffies;
- __update_cpu_load(this_rq, this_rq->load.weight, 1);
+ __update_cpu_load(this_rq, load, 1);

calc_load_account_active(this_rq);
}
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2881d42..407ef61 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2900,7 +2900,8 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
- return cpu_rq(cpu)->load.weight;
+ struct rq *rq = cpu_rq(cpu);
+ return rq->cfs.runnable_load_avg + rq->cfs.blocked_load_avg;
}

/*
@@ -2946,8 +2947,11 @@ static unsigned long cpu_avg_load_per_task(int cpu)
struct rq *rq = cpu_rq(cpu);
unsigned long nr_running = ACCESS_ONCE(rq->nr_running);

+ unsigned long load_avg;
+ load_avg = rq->cfs.runnable_load_avg + rq->cfs.blocked_load_avg;
+
if (nr_running)
- return rq->load.weight / nr_running;
+ return load_avg / nr_running;

return 0;
}
--
1.7.12

--
Thanks
Alex


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