Re: [PATCH v4 6/6] sched: consider runnable load average in effective_load

Alex Shi
2013-05-03T07:40:30Z

On 05/02/2013 09:19 PM, Peter Zijlstra wrote:
>
> I'm fairly sure this is wrong; but I haven't bothered to take pencil to paper.
>
> I think you'll need to insert the runnable avg load and make sure
> effective_load() uses the right sums itself.

Thanks for comment!
I changed it to the following patch for further review.
a quick testing show hackbench still keep the improvement.

Will resent a new version to include all changes. :)

---

>From 2f6491807226a30e01b9afa21d80e42e7cbb5678 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@intel.com>
Date: Fri, 3 May 2013 13:29:04 +0800
Subject: [PATCH 7/8] sched: consider runnable load average in effective_load

effective_load calculates the load change as seen from the
root_task_group. It needs to engage the runnable average
of changed task.

Thanks for Morten Rasmussen and PeterZ's reminder of this.

Signed-off-by: Alex Shi <alex.shi@intel.com>
---
kernel/sched/fair.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 790e23d..6f4f14b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2976,15 +2976,15 @@ static void task_waking_fair(struct task_struct *p)

#ifdef CONFIG_FAIR_GROUP_SCHED
/*
- * effective_load() calculates the load change as seen from the root_task_group
+ * effective_load() calculates load avg change as seen from the root_task_group
*
* Adding load to a group doesn't make a group heavier, but can cause movement
* of group shares between cpus. Assuming the shares were perfectly aligned one
* can calculate the shift in shares.
*
- * Calculate the effective load difference if @wl is added (subtracted) to @tg
- * on this @cpu and results in a total addition (subtraction) of @wg to the
- * total group weight.
+ * Calculate the effective load avg difference if @wl is added (subtracted) to
+ * @tg on this @cpu and results in a total addition (subtraction) of @wg to the
+ * total group load avg.
*
* Given a runqueue weight distribution (rw_i) we can compute a shares
* distribution (s_i) using:
@@ -2998,7 +2998,7 @@ static void task_waking_fair(struct task_struct *p)
* rw_i = { 2, 4, 1, 0 }
* s_i = { 2/7, 4/7, 1/7, 0 }
*
- * As per wake_affine() we're interested in the load of two CPUs (the CPU the
+ * As per wake_affine() we're interested in load avg of two CPUs (the CPU the
* task used to run on and the CPU the waker is running on), we need to
* compute the effect of waking a task on either CPU and, in case of a sync
* wakeup, compute the effect of the current task going to sleep.
@@ -3008,20 +3008,20 @@ static void task_waking_fair(struct task_struct *p)
*
* s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
*
- * Suppose we're interested in CPUs 0 and 1, and want to compute the load
+ * Suppose we're interested in CPUs 0 and 1, and want to compute the load avg
* differences in waking a task to CPU 0. The additional task changes the
* weight and shares distributions like:
*
* rw'_i = { 3, 4, 1, 0 }
* s'_i = { 3/8, 4/8, 1/8, 0 }
*
- * We can then compute the difference in effective weight by using:
+ * We can then compute the difference in effective load avg by using:
*
* dw_i = S * (s'_i - s_i) (3)
*
* Where 'S' is the group weight as seen by its parent.
*
- * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
+ * Therefore the effective change in load avg on CPU 0 would be 5/56 (3/8 - 2/7)
* times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
* 4/7) times the weight of the group.
*/
@@ -3045,7 +3045,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
/*
* w = rw_i + @wl
*/
- w = se->my_q->load.weight + wl;
+ w = se->my_q->tg_load_contrib + wl;

/*
* wl = S * s'_i; see (2)
@@ -3066,7 +3066,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
/*
* wl = dw_i = S * (s'_i - s_i); see (3)
*/
- wl -= se->load.weight;
+ wl -= se->avg.load_avg_contrib;

/*
* Recursively apply this logic to all parent groups to compute
@@ -3112,14 +3112,14 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
*/
if (sync) {
tg = task_group(current);
- weight = current->se.load.weight;
+ weight = current->se.avg.load_avg_contrib;

this_load += effective_load(tg, this_cpu, -weight, -weight);
load += effective_load(tg, prev_cpu, 0, -weight);
}

tg = task_group(p);
- weight = p->se.load.weight;
+ weight = p->se.avg.load_avg_contrib;

/*
* In low-load situations, where prev_cpu is idle and this_cpu is idle
--
1.7.12

--
Thanks
Alex