Hi Alex,Michael,
Can you try out the below patch and check? I have the reason mentioned in the
changelog.
If this also causes performance regression,you probably need to remove changes
made in
effective_load() as Michael points out. I believe the below patch should not
cause
performance regression.
The below patch is a substitute for patch 7.
-------------------------------------------------------------------------------
sched: Modify effective_load() to use runnable load average
From: Preeti U Murthy <pre...@linux.vnet.ibm.com>
The runqueue weight distribution should update the runnable load average of
the cfs_rq on which the task will be woken up.
However since the computation of se->load.weight takes into consideration
the runnable load average in update_cfs_shares(),no need to modify this in
effective_load().
---
kernel/sched/fair.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 790e23d..5489022 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -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->runnable_load_avg + wl;
/*
* wl = S * s'_i; see (2)
@@ -3066,6 +3066,9 @@ static long effective_load(struct task_group *tg, int
cpu, long wl, long wg)
/*
* wl = dw_i = S * (s'_i - s_i); see (3)
*/
+ /* Do not modify the below as it already contains runnable
+ * load average in its computation
+ */
wl -= se->load.weight;
/*
@@ -3112,14 +3115,14 @@ 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
Regards
Preeti U Murthy
On 05/06/2013 09:04 AM, Michael Wang wrote:
> Hi, Alex
>
> On 05/06/2013 09:45 AM, Alex Shi wrote:
>> effective_load calculates the load change as seen from the
>> root_task_group. It needs to engage the runnable average
>> of changed task.
> [snip]
>> */
>> @@ -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;
>
> I've tested the patch set, seems like the last patch caused big
> regression on pgbench:
>
> base patch 1~6 patch 1~7
> | db_size | clients | tps | | tps | | tps |
> +---------+---------+-------+ +-------+ +-------+
> | 22 MB | 32 | 43420 | | 53387 | | 41625 |
>
> I guess some magic thing happened in effective_load() while calculating
> group decay combined with load decay, what's your opinion?
>
> Regards,
> Michael Wang
>
>>
>> /*
>> * 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
>>
>
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