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sched: cgroup: Implement different treatment for idle shares

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When setting the weight for a per-cpu task-group, we have to put in a
phantom weight when there is no work on that cpu, otherwise we'll not
service that cpu when new work gets placed there until we again update
the per-cpu weights.

We used to add these phantom weights to the total, so that the idle
per-cpu shares don't get inflated, this however causes the non-idle
parts to get deflated, causing unexpected weight distibutions.

Reverse this, so that the non-idle shares are correct but the idle
shares are inflated.

Reported-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Tested-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1257934048.23203.76.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-12-03 18:00:07 +01:00 committed by Ingo Molnar
parent fb58bac5c7
commit cd8ad40de3
1 changed files with 6 additions and 2 deletions
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8
kernel/sched.c
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@ -1614,7 +1614,7 @@ static void update_group_shares_cpu(struct task_group *tg, int cpu,
*/
static int tg_shares_up(struct task_group *tg, void *data)
{
unsigned long weight, rq_weight = 0, shares = 0;
unsigned long weight, rq_weight = 0, sum_weight = 0, shares = 0;
unsigned long *usd_rq_weight;
struct sched_domain *sd = data;
unsigned long flags;
@ -1630,6 +1630,7 @@ static int tg_shares_up(struct task_group *tg, void *data)
weight = tg->cfs_rq[i]->load.weight;
usd_rq_weight[i] = weight;
rq_weight += weight;
/*
* If there are currently no tasks on the cpu pretend there
* is one of average load so that when a new task gets to
@ -1638,10 +1639,13 @@ static int tg_shares_up(struct task_group *tg, void *data)
if (!weight)
weight = NICE_0_LOAD;
rq_weight += weight;
sum_weight += weight;
shares += tg->cfs_rq[i]->shares;
}
if (!rq_weight)
rq_weight = sum_weight;
if ((!shares && rq_weight) || shares > tg->shares)
shares = tg->shares;