[01/34] sched: cgroup: Implement different treatment for idle shares

From: Greg KH
Date: Fri Aug 06 2010 - 15:16:08 EST

2.6.32-stable review patch. If anyone has any objections, please let us know.


From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>

commit cd8ad40de36c2fe75f3b731bd70198b385895246 upstream.

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@xxxxxxxxxxxxxx>
Tested-by: Yasunori Goto <y-goto@xxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
LKML-Reference: <1257934048.23203.76.camel@twins>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

kernel/sched.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1623,7 +1623,7 @@ static void update_group_shares_cpu(stru
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;
@@ -1639,6 +1639,7 @@ static int tg_shares_up(struct task_grou
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
@@ -1647,10 +1648,13 @@ static int tg_shares_up(struct task_grou
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;

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