On Thu, 2013-02-14 at 14:48 +0900, Joonsoo Kim wrote:
> Some validation for task moving is performed in move_tasks() and
> move_one_task(). We can move these code to can_migrate_task()
> which is already exist for this purpose.
> @@ -4011,18 +4027,7 @@ static int move_tasks(struct lb_env *env)
> break;
> }
>
> - if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
> - goto next;
> -
> - load = task_h_load(p);
> -
> - if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
> - goto next;
> -
> - if ((load / 2) > env->imbalance)
> - goto next;
> -
> - if (!can_migrate_task(p, env))
> + if (!can_migrate_task(p, env, false, &load))
> goto next;
>
> move_task(p, env);
Right, so I'm not so taken with this one. The whole load stuff really
is a balance heuristic that's part of move_tasks(), move_one_task()
really doesn't care about that.
So why did you include it? Purely so you didn't have to re-order the
tests? I don't see any reason not to flip a tests around.
On Tue, Mar 19, 2013 at 03:30:15PM +0100, Peter Zijlstra wrote:
> On Thu, 2013-02-14 at 14:48 +0900, Joonsoo Kim wrote:
> > Some validation for task moving is performed in move_tasks() and
> > move_one_task(). We can move these code to can_migrate_task()
> > which is already exist for this purpose.
>
> > @@ -4011,18 +4027,7 @@ static int move_tasks(struct lb_env *env)
> > break;
> > }
> >
> > - if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
> > - goto next;
> > -
> > - load = task_h_load(p);
> > -
> > - if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
> > - goto next;
> > -
> > - if ((load / 2) > env->imbalance)
> > - goto next;
> > -
> > - if (!can_migrate_task(p, env))
> > + if (!can_migrate_task(p, env, false, &load))
> > goto next;
> >
> > move_task(p, env);
>
> Right, so I'm not so taken with this one. The whole load stuff really
> is a balance heuristic that's part of move_tasks(), move_one_task()
> really doesn't care about that.
>
> So why did you include it? Purely so you didn't have to re-order the
> tests? I don't see any reason not to flip a tests around.
I think that I'm not fully understand what you are concerning, because of
my poor English. If possible, please elaborate on a problem in more detail.
First of all, I do my best to answer your question.
Patch 4/8, 5/8 are for mitigating useless redoing overhead caused
by LBF_ALL_PINNED. For this purpose, we should check 'cpu affinity'
before evaluating a load. Just moving up can_migrate_task() above
load evaluation code may raise side effect, because can_migrate_task() have
other checking which is 'cache hottness'. I don't want a side effect. So
embedding load evaluation to can_migrate_task() and re-order checking and
makes load evaluation disabled for move_one_task().
If your recommandation is to move up can_mirate_task() above
load evaluation code, yes, I can, and will do that. :)
Please let me know what I am misunderstand.
Thanks.
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On Wed, 2013-03-20 at 16:33 +0900, Joonsoo Kim wrote:
> > Right, so I'm not so taken with this one. The whole load stuff really
> > is a balance heuristic that's part of move_tasks(), move_one_task()
> > really doesn't care about that.
> >
> > So why did you include it? Purely so you didn't have to re-order the
> > tests? I don't see any reason not to flip a tests around.
>
> I think that I'm not fully understand what you are concerning, because of
> my poor English. If possible, please elaborate on a problem in more detail.
OK, so your initial Changelog said it wanted to remove some code
duplication between move_tasks() and move_one_task(); but then you put
in the load heuristics and add a boolean argument to only enable those
for move_tasks() -- so clearly that wasn't duplicated.
So why move that code.. I proposed that this was due a reluctance to
re-arrange the various tests that stop the migration from happening.
Now you say:
> ... Just moving up can_migrate_task() above
> load evaluation code may raise side effect, because can_migrate_task() have
> other checking which is 'cache hottness'. I don't want a side effect. So
> embedding load evaluation to can_migrate_task() and re-order checking and
> makes load evaluation disabled for move_one_task().
Which pretty much affirms this. However I also said that I don't think
the order really matters that much; each test will cancel the migration
of this task; the order of these tests seem immaterial.
> If your recommandation is to move up can_mirate_task() above
> load evaluation code, yes, I can, and will do that. :)
I would actually propose moving the throttled test into
can_migrate_task() and leave it at that.
On Wed, 2013-03-20 at 16:33 +0900, Joonsoo Kim wrote:
> > Right, so I'm not so taken with this one. The whole load stuff really
> > is a balance heuristic that's part of move_tasks(), move_one_task()
> > really doesn't care about that.
> >
> > So why did you include it? Purely so you didn't have to re-order the
> > tests? I don't see any reason not to flip a tests around.
>
> I think that I'm not fully understand what you are concerning, because of
> my poor English. If possible, please elaborate on a problem in more detail.
OK, so your initial Changelog said it wanted to remove some code
duplication between move_tasks() and move_one_task(); but then you put
in the load heuristics and add a boolean argument to only enable those
for move_tasks() -- so clearly that wasn't duplicated.
So why move that code.. I proposed that this was due a reluctance to
re-arrange the various tests that stop the migration from happening.
Now you say:
> ... Just moving up can_migrate_task() above
> load evaluation code may raise side effect, because can_migrate_task() have
> other checking which is 'cache hottness'. I don't want a side effect. So
> embedding load evaluation to can_migrate_task() and re-order checking and
> makes load evaluation disabled for move_one_task().
Which pretty much affirms this. However I also said that I don't think
the order really matters that much; each test will cancel the migration
of this task; the order of these tests seem immaterial.
> If your recommandation is to move up can_mirate_task() above
> load evaluation code, yes, I can, and will do that. :)
I would actually propose
On Wed, 2013-03-20 at 12:16 +0100, Peter Zijlstra wrote:
> > If your recommandation is to move up can_mirate_task() above
> > load evaluation code, yes, I can, and will do that. :)
>
> I would actually propose
... to move the throttled test into can_migrate_task().
(damn evo crashed on me... *again*).
2013/3/20 Peter Zijlstra <[email protected]>:
> On Wed, 2013-03-20 at 16:33 +0900, Joonsoo Kim wrote:
>
>> > Right, so I'm not so taken with this one. The whole load stuff really
>> > is a balance heuristic that's part of move_tasks(), move_one_task()
>> > really doesn't care about that.
>> >
>> > So why did you include it? Purely so you didn't have to re-order the
>> > tests? I don't see any reason not to flip a tests around.
>>
>> I think that I'm not fully understand what you are concerning, because of
>> my poor English. If possible, please elaborate on a problem in more detail.
>
> OK, so your initial Changelog said it wanted to remove some code
> duplication between move_tasks() and move_one_task(); but then you put
> in the load heuristics and add a boolean argument to only enable those
> for move_tasks() -- so clearly that wasn't duplicated.
>
> So why move that code.. I proposed that this was due a reluctance to
> re-arrange the various tests that stop the migration from happening.
>
> Now you say:
>
>> ... Just moving up can_migrate_task() above
>> load evaluation code may raise side effect, because can_migrate_task() have
>> other checking which is 'cache hottness'. I don't want a side effect. So
>> embedding load evaluation to can_migrate_task() and re-order checking and
>> makes load evaluation disabled for move_one_task().
>
> Which pretty much affirms this. However I also said that I don't think
> the order really matters that much; each test will cancel the migration
> of this task; the order of these tests seem immaterial.
>
>> If your recommandation is to move up can_mirate_task() above
>> load evaluation code, yes, I can, and will do that. :)
>
> I would actually propose moving the throttled test into
> can_migrate_task() and leave it at that.
Okay. I will do that in next spin.
Thanks!!
>
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