Messages in this thread | | | Date | Fri, 11 Jan 2013 11:26:59 +0800 | From | Alex Shi <> | Subject | Re: [PATCH v3 11/22] sched: consider runnable load average in effective_load |
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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. >> >> 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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