Messages in this thread Patch in this message | | | Date | Mon, 14 Jan 2013 12:01:39 +0000 | From | Morten Rasmussen <> | Subject | Re: [PATCH v3 11/22] sched: consider runnable load average in effective_load |
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On Fri, Jan 11, 2013 at 03:26:59AM +0000, Alex Shi wrote: > On 01/10/2013 07:28 PM, Morten Rasmussen wrote: > > On Sat, Jan 05, 2013 at 08:37:40AM +0000, Alex Shi wrote: > >> effective_load calculates the load change as seen from the > >> root_task_group. It needs to multiple cfs_rq's tg_runnable_contrib > >> when we turn to runnable load average balance. > >> > >> Signed-off-by: Alex Shi <alex.shi@intel.com> > >> --- > >> kernel/sched/fair.c | 11 ++++++++--- > >> 1 file changed, 8 insertions(+), 3 deletions(-) > >> > >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > >> index cab62aa..247d6a8 100644 > >> --- a/kernel/sched/fair.c > >> +++ b/kernel/sched/fair.c > >> @@ -2982,7 +2982,8 @@ 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 the runnable load average 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 > >> @@ -3030,13 +3031,17 @@ static void task_waking_fair(struct task_struct *p) > >> * Therefore the effective change in loads 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. > >> + * > >> + * After get effective_load of the load moving, will multiple the cpu own > >> + * cfs_rq's runnable contrib of root_task_group. > >> */ > >> static long effective_load(struct task_group *tg, int cpu, long wl, long wg) > >> { > >> struct sched_entity *se = tg->se[cpu]; > >> > >> if (!tg->parent) /* the trivial, non-cgroup case */ > >> - return wl; > >> + return wl * tg->cfs_rq[cpu]->tg_runnable_contrib > >> + >> NICE_0_SHIFT; > > > > Why do we need to scale the load of the task (wl) by runnable_contrib > > when the task is in the root task group? Wouldn't the load change still > > just be wl? > > > > Here, wl is the load weight, runnable_contrib engaged the runnable time.
Yes, wl is the load weight of the task. But I don't understand why you multiply it with the tg_runnable_contrib of the group you want to insert it into. Since effective_load() is supposed to return the load change caused by adding the task to the cpu it would make more sense if you multiplied with the task runnable_avg_sum / runnable_avg_period of the task in question.
Morten
> >> > >> for_each_sched_entity(se) { > >> long w, W; > >> @@ -3084,7 +3089,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg) > >> wg = 0; > >> } > >> > >> - return wl; > >> + return wl * tg->cfs_rq[cpu]->tg_runnable_contrib >> NICE_0_SHIFT; > > > > I believe that effective_load() is only used in wake_affine() to compare > > load scenarios of the same task group. Since the task group is the same > > the effective load is scaled by the same factor and should not make any > > difference? > > > > Also, in wake_affine() the result of effective_load() is added with > > target_load() which is load.weight of the cpu and not a tracked load > > based on runnable_avg_*/contrib? > > > > Finally, you have not scaled the result of effective_load() in the > > function used when FAIR_GROUP_SCHED is disabled. Should that be scaled > > too? > > it should be, thanks reminder. > > the wake up is not good for burst wakeup benchmark. I am thinking to > rewrite this part. > >
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