On 8/10/15 10:10 PM, Juri Lelli wrote:
On 06/08/15 09:39, Wanpeng Li wrote:
Hi Juri,
Hi,
2015-05-06 16:14 GMT+08:00 Juri Lelli <juri.le...@arm.com
<mailto:juri.le...@arm.com>>:
Hi Wanpeng,
I finally got to review this, sorry about the huge delay.
On 07/04/2015 04:36, Wanpeng Li wrote:
> The total used dl bandwidth of each root domain will be reset to 0 after
> cpu hotplug when rebuild sched domains, since the call path is:
>
> _cpu_down
> cpuset_cpu_inactive()
> cpuset_update_active_cpus()
> partition_sched_domains()
> build_sched_domains()
> init_rootdomain()
> init_dl_bw()
>
> The bandwidth which dl task occupy will be released when dl task dead,
> it will be minus from total used dl bandwidth of its root domain,
> however, bandwidth overflow occurs since total used dl bandwidth is 0.
>
Right, that's a bug.
> This patch fix it by attaching the bandwidth which dl task occupy to
> the new root domain when the task is migrating since cpu hotplug, and
> attach all the used dl bandwidth of dl tasks to the new root domain
> when sched domains are rebuild.
>
But, I think this fix has still a couple of problems:
- what happens if a DL task is simply sleeping when domains are
reconfigured?
- def_root_domain has now multiple accounting problems, as you do
this thing even when a cpu is moved there in the cpuoff path
Also, runqueue (and throttling) information are dynamic, while we
are trying to fix a static problem. It's probably not a good idea
mixing them.
I'm not sure how (I need more time to think it through), but can
we maybe fix this using cpuset information?
Any ideas?
Yes, actually. I might have a different fix, but I'd like to play with
it a bit more as it is a bit too intrusive. Let me see if I can come
up with something that I can share.
Ping Peter, Juri, any detail ideas to help me post another version of my
patch? ;-)
Regards,
Wanpeng Li
Thanks,
- Juri
Regards,
Wanpeng Li
Thanks,
- Juri
> Signed-off-by: Wanpeng Li <wanpeng...@linux.intel.com
<mailto:wanpeng...@linux.intel.com>>
> ---
> kernel/sched/core.c | 1 +
> kernel/sched/deadline.c | 25 +++++++++++++++++++++++++
> kernel/sched/sched.h | 1 +
> 3 files changed, 27 insertions(+)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 28b0d75..c940999 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5586,6 +5586,7 @@ static void rq_attach_root(struct rq *rq,
struct root_domain *rd)
> rq->rd = rd;
>
> cpumask_set_cpu(rq->cpu, rd->span);
> + attach_dl_bw(rq);
> if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
> set_rq_online(rq);
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 5e95145..62680d7 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -224,6 +224,7 @@ static void dl_task_offline_migration(struct
rq *rq, struct task_struct *p)
> {
> struct rq *later_rq = NULL;
> bool fallback = false;
> + struct dl_bw *dl_b;
>
> later_rq = find_lock_later_rq(p, rq);
>
> @@ -258,6 +259,11 @@ static void dl_task_offline_migration(struct
rq *rq, struct task_struct *p)
> set_task_cpu(p, later_rq->cpu);
> activate_task(later_rq, p, ENQUEUE_REPLENISH);
>
> + dl_b = dl_bw_of(later_rq->cpu);
> + raw_spin_lock(&dl_b->lock);
> + __dl_add(dl_b, p->dl.dl_bw);
> + raw_spin_unlock(&dl_b->lock);
> +
> if (!fallback)
> resched_curr(later_rq);
>
> @@ -1776,6 +1782,25 @@ static void prio_changed_dl(struct rq *rq,
struct task_struct *p,
> switched_to_dl(rq, p);
> }
>
> +void attach_dl_bw(struct rq *rq)
> +{
> + struct rb_node *next_node = rq->dl.rb_leftmost;
> + struct sched_dl_entity *dl_se;
> + struct dl_bw *dl_b;
> +
> + dl_b = dl_bw_of(rq->cpu);
> + raw_spin_lock(&dl_b->lock);
> +next_node:
> + if (next_node) {
> + dl_se = rb_entry(next_node, struct sched_dl_entity,
rb_node);
> + __dl_add(dl_b, dl_se->dl_bw);
> + next_node = rb_next(next_node);
> +
> + goto next_node;
> + }
> + raw_spin_unlock(&dl_b->lock);
> +}
> +
> const struct sched_class dl_sched_class = {
> .next = &rt_sched_class,
> .enqueue_task = enqueue_task_dl,
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index e0e1299..a7b1a59 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1676,6 +1676,7 @@ extern void init_dl_rq(struct dl_rq *dl_rq);
>
> extern void cfs_bandwidth_usage_inc(void);
> extern void cfs_bandwidth_usage_dec(void);
> +void attach_dl_bw(struct rq *rq);
>
> #ifdef CONFIG_NO_HZ_COMMON
> enum rq_nohz_flag_bits {
>
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