lkml.org 
[lkml]   [2013]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: [PATCH v3 11/22] sched: consider runnable load average in effective_load
    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.
    >
    >



    \
     
     \ /
      Last update: 2013-01-14 13:43    [W:5.503 / U:0.024 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site