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Date: Fri, 20 Dec 2013 22:44:13 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: tglx@...utronix.de, mingo@...hat.com, oleg@...hat.com,
fweisbec@...il.com, darren@...art.com, johan.eker@...csson.com,
p.faure@...tech.ch, linux-kernel@...r.kernel.org,
claudio@...dence.eu.com, michael@...rulasolutions.com,
fchecconi@...il.com, tommaso.cucinotta@...up.it,
juri.lelli@...il.com, nicola.manica@...i.unitn.it,
luca.abeni@...tn.it, dhaval.giani@...il.com, hgu1972@...il.com,
paulmck@...ux.vnet.ibm.com, raistlin@...ux.it,
insop.song@...il.com, liming.wang@...driver.com, jkacur@...hat.com
Subject: Re: [PATCH 09/13] sched: Add bandwidth management for sched_dl
On Fri, Dec 20, 2013 at 01:23:23PM -0500, Steven Rostedt wrote:
> I'm saying what stops this?
oh duh, yes.
So the below is a bit cumbersome in having to use rd->span &
cpu_active_mask because it appears rd->online is too late again.
So I think this will avoid the problem by being consistent with the cpu
count. At worst it will reject a new task that could've fit, but that's
a safe mistake to make.
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1886,9 +1886,15 @@ inline struct dl_bw *dl_bw_of(int i)
return &cpu_rq(i)->rd->dl_bw;
}
-static inline int __dl_span_weight(struct rq *rq)
+static inline int dl_bw_cpus(int i)
{
- return cpumask_weight(rq->rd->span);
+ struct root_domain *rd = cpu_rq(i)->rd;
+ int cpus = 0;
+
+ for_each_cpu_and(rd->span, cpu_active_mask)
+ cpus++;
+
+ return cpus;
}
#else
inline struct dl_bw *dl_bw_of(int i)
@@ -1896,7 +1902,7 @@ inline struct dl_bw *dl_bw_of(int i)
return &cpu_rq(i)->dl.dl_bw;
}
-static inline int __dl_span_weight(struct rq *rq)
+static inline int dl_bw_cpus(int i)
{
return 1;
}
@@ -1937,8 +1943,7 @@ static int dl_overflow(struct task_struc
u64 period = attr->sched_period;
u64 runtime = attr->sched_runtime;
u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
- int cpus = __dl_span_weight(task_rq(p));
- int err = -1;
+ int cpus, err = -1;
if (new_bw == p->dl.dl_bw)
return 0;
@@ -1949,6 +1954,7 @@ static int dl_overflow(struct task_struc
* allocated bandwidth of the container.
*/
raw_spin_lock(&dl_b->lock);
+ cpus = dl_bw_cpus(task_cpu(p));
if (dl_policy(policy) && !task_has_dl_policy(p) &&
!__dl_overflow(dl_b, cpus, 0, new_bw)) {
__dl_add(dl_b, new_bw);
@@ -4523,42 +4529,6 @@ int set_cpus_allowed_ptr(struct task_str
EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
/*
- * When dealing with a -deadline task, we have to check if moving it to
- * a new CPU is possible or not. In fact, this is only true iff there
- * is enough bandwidth available on such CPU, otherwise we want the
- * whole migration procedure to fail over.
- */
-static inline
-bool set_task_cpu_dl(struct task_struct *p, unsigned int cpu)
-{
- struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
- struct dl_bw *cpu_b = dl_bw_of(cpu);
- int ret = 1;
- u64 bw;
-
- if (dl_b == cpu_b)
- return 1;
-
- raw_spin_lock(&dl_b->lock);
- raw_spin_lock(&cpu_b->lock);
-
- bw = cpu_b->bw * cpumask_weight(cpu_rq(cpu)->rd->span);
- if (dl_bandwidth_enabled() &&
- bw < cpu_b->total_bw + p->dl.dl_bw) {
- ret = 0;
- goto unlock;
- }
- dl_b->total_bw -= p->dl.dl_bw;
- cpu_b->total_bw += p->dl.dl_bw;
-
-unlock:
- raw_spin_unlock(&cpu_b->lock);
- raw_spin_unlock(&dl_b->lock);
-
- return ret;
-}
-
-/*
* Move (not current) task off this cpu, onto dest cpu. We're doing
* this because either it can't run here any more (set_cpus_allowed()
* away from this CPU, or CPU going down), or because we're
@@ -4590,13 +4560,6 @@ static int __migrate_task(struct task_st
goto fail;
/*
- * If p is -deadline, proceed only if there is enough
- * bandwidth available on dest_cpu
- */
- if (unlikely(dl_task(p)) && !set_task_cpu_dl(p, dest_cpu))
- goto fail;
-
- /*
* If we're not on a rq, the next wake-up will ensure we're
* placed properly.
*/
@@ -4986,7 +4949,6 @@ migration_call(struct notifier_block *nf
struct rq *rq = cpu_rq(cpu);
switch (action & ~CPU_TASKS_FROZEN) {
-
case CPU_UP_PREPARE:
rq->calc_load_update = calc_load_update;
break;
@@ -5056,10 +5018,28 @@ static int sched_cpu_inactive(struct not
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
set_cpu_active((long)hcpu, false);
- return NOTIFY_OK;
- default:
- return NOTIFY_DONE;
+ break;
}
+
+ switch (action) {
+ case CPU_DOWN_PREPARE: /* explicitly allow suspend */
+ {
+ struct dl_bw *dl_b = dl_bw_of(cpu);
+ bool overflow;
+ int cpus;
+
+ raw_spin_lock_irqsave(&dl_b->lock, flags);
+ cpus = dl_bw_cpus(cpu);
+ overflow = __dl_overflow(dl_b, cpus, 0, 0);
+ raw_spin_unlock_irqrestore(&dl_b->lock, flags);
+
+ if (overflow)
+ return notifier_from_errno(-EBUSY);
+ }
+ break;
+ }
+
+ return NOTIFY_OK;
}
static int __init migration_init(void)
--
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