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SubjectRe: [RT] [PATCH] Make scheduler root_domain modular (sched_classspecific)
Hi Gregory,

On Sat, Mar 22, 2008 at 12:04:04PM -0600, Gregory Haskins wrote:
> >>> On Sat, Mar 22, 2008 at 10:29 AM, in message
> <20080322142915.GA9478@in.ibm.com>, Ankita Garg <ankita@in.ibm.com> wrote:
> > Hello,
> >
> > Thanks Gregory for clarifying my question on root_domains infrastructure.
> > What
> > I was effectively mentioning on irc the other day was to make the
> > root_domain
> > infrastructure modular, ie sched_class specific. Currently, only rt is
> > making
> > use of this infrasture. Making it modular would enable ease of extension to
> > other sched_classes if required. Trivial patch to that effect.
> >
> > Patch compile and boot tested.
>
> Hi Ankita,
> Very nice, thanks! Couple of minor nits and further cleanup opportunities inline, but otherwise:
>
> Acked-by: Gregory Haskins <ghaskins@novell.com>
>
> >
The changes you have suggested are consistent with what we do for rt_rq
and cfs_rq. Here is the patch with these modifications.


Signed-off-by: Ankita Garg <ankita@in.ibm.com>

Index: linux-2.6.24.3-rt3/kernel/sched.c
===================================================================
--- linux-2.6.24.3-rt3.orig/kernel/sched.c 2008-03-21 22:57:04.000000000 +0530
+++ linux-2.6.24.3-rt3/kernel/sched.c 2008-03-23 14:09:22.000000000 +0530
@@ -337,22 +337,27 @@
* object.
*
*/
-struct root_domain {
- atomic_t refcount;
- cpumask_t span;
- cpumask_t online;

+struct rt_root_domain {
/*
* The "RT overload" flag: it gets set if a CPU has more than
* one runnable RT task.
*/
- cpumask_t rto_mask;
- atomic_t rto_count;
+ cpumask_t overload_mask;
+ atomic_t overload_count;
#ifdef CONFIG_SMP
struct cpupri cpupri;
#endif
};

+struct root_domain {
+ atomic_t refcount;
+ cpumask_t span;
+ cpumask_t online;
+
+ struct rt_root_domain rt;
+};
+
/*
* By default the system creates a single root-domain with all cpus as
* members (mimicking the global state we have today).
@@ -6332,7 +6337,7 @@
cpus_clear(rd->span);
cpus_clear(rd->online);

- cpupri_init(&rd->cpupri);
+ cpupri_init(&rd->rt.cpupri);

}

Index: linux-2.6.24.3-rt3/kernel/sched_rt.c
===================================================================
--- linux-2.6.24.3-rt3.orig/kernel/sched_rt.c 2008-03-21 22:57:04.000000000 +0530
+++ linux-2.6.24.3-rt3/kernel/sched_rt.c 2008-03-23 14:12:45.000000000 +0530
@@ -7,12 +7,12 @@

static inline int rt_overloaded(struct rq *rq)
{
- return atomic_read(&rq->rd->rto_count);
+ return atomic_read(&rq->rd->rt.overload_count);
}

static inline void rt_set_overload(struct rq *rq)
{
- cpu_set(rq->cpu, rq->rd->rto_mask);
+ cpu_set(rq->cpu, rq->rd->rt.overload_mask);
/*
* Make sure the mask is visible before we set
* the overload count. That is checked to determine
@@ -21,14 +21,14 @@
* updated yet.
*/
wmb();
- atomic_inc(&rq->rd->rto_count);
+ atomic_inc(&rq->rd->rt.overload_count);
}

static inline void rt_clear_overload(struct rq *rq)
{
/* the order here really doesn't matter */
- atomic_dec(&rq->rd->rto_count);
- cpu_clear(rq->cpu, rq->rd->rto_mask);
+ atomic_dec(&rq->rd->rt.overload_count);
+ cpu_clear(rq->cpu, rq->rd->rt.overload_mask);
}

static void update_rt_migration(struct rq *rq)
@@ -78,7 +78,7 @@
#ifdef CONFIG_SMP
if (p->prio < rq->rt.highest_prio) {
rq->rt.highest_prio = p->prio;
- cpupri_set(&rq->rd->cpupri, rq->cpu, p->prio);
+ cpupri_set(&rq->rd->rt.cpupri, rq->cpu, p->prio);
}
if (p->nr_cpus_allowed > 1)
rq->rt.rt_nr_migratory++;
@@ -114,7 +114,7 @@
}

if (rq->rt.highest_prio != highest_prio)
- cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio);
+ cpupri_set(&rq->rd->rt.cpupri, rq->cpu, rq->rt.highest_prio);

update_rt_migration(rq);
#endif /* CONFIG_SMP */
@@ -363,7 +363,7 @@
{
int count;

- count = cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask);
+ count = cpupri_find(&task_rq(task)->rd->rt.cpupri, task, lowest_mask);

/*
* cpupri cannot efficiently tell us how many bits are set, so it only
@@ -599,7 +599,7 @@

next = pick_next_task_rt(this_rq);

- for_each_cpu_mask(cpu, this_rq->rd->rto_mask) {
+ for_each_cpu_mask(cpu, this_rq->rd->rt.overload_mask) {
if (this_cpu == cpu)
continue;

@@ -763,7 +763,7 @@
if (rq->rt.overloaded)
rt_set_overload(rq);

- cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio);
+ cpupri_set(&rq->rd->rt.cpupri, rq->cpu, rq->rt.highest_prio);
}

/* Assumes rq->lock is held */
@@ -772,7 +772,7 @@
if (rq->rt.overloaded)
rt_clear_overload(rq);

- cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
+ cpupri_set(&rq->rd->rt.cpupri, rq->cpu, CPUPRI_INVALID);
}

/*
--
Regards,
Ankita Garg (ankita@in.ibm.com)
Linux Technology Center
IBM India Systems & Technology Labs,
Bangalore, India


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