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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v4 40/46] xen/sched: split schedule_cpu_switch()
Instead of letting schedule_cpu_switch() handle moving cpus from and
to cpupools, split it into schedule_cpu_add() and schedule_cpu_rm().
This will allow us to drop allocating/freeing scheduler data for free
cpus as the idle scheduler doesn't need such data.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V1: new patch
V4:
- rename sd -> sr (Jan Beulich)
---
xen/common/cpupool.c | 4 +-
xen/common/schedule.c | 133 +++++++++++++++++++++++++++---------------------
xen/include/xen/sched.h | 3 +-
3 files changed, 78 insertions(+), 62 deletions(-)
diff --git a/xen/common/cpupool.c b/xen/common/cpupool.c
index 51f0ff0d88..02825e779d 100644
--- a/xen/common/cpupool.c
+++ b/xen/common/cpupool.c
@@ -271,7 +271,7 @@ static int cpupool_assign_cpu_locked(struct cpupool *c,
unsigned int cpu)
if ( (cpupool_moving_cpu == cpu) && (c != cpupool_cpu_moving) )
return -EADDRNOTAVAIL;
- ret = schedule_cpu_switch(cpu, c);
+ ret = schedule_cpu_add(cpu, c);
if ( ret )
return ret;
@@ -321,7 +321,7 @@ static int cpupool_unassign_cpu_finish(struct cpupool *c)
*/
if ( !ret )
{
- ret = schedule_cpu_switch(cpu, NULL);
+ ret = schedule_cpu_rm(cpu);
if ( ret )
cpumask_clear_cpu(cpu, &cpupool_free_cpus);
else
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 63ffe1a824..c75ec969c2 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -91,15 +91,6 @@ static struct scheduler __read_mostly ops;
static void sched_set_affinity(
struct sched_unit *unit, const cpumask_t *hard, const cpumask_t *soft);
-static spinlock_t *
-sched_idle_switch_sched(struct scheduler *new_ops, unsigned int cpu,
- void *pdata, void *vdata)
-{
- sched_idle_unit(cpu)->priv = NULL;
-
- return &sched_free_cpu_lock;
-}
-
static struct sched_resource *
sched_idle_res_pick(const struct scheduler *ops, const struct sched_unit *unit)
{
@@ -139,7 +130,6 @@ static struct scheduler sched_idle_ops = {
.alloc_udata = sched_idle_alloc_udata,
.free_udata = sched_idle_free_udata,
- .switch_sched = sched_idle_switch_sched,
};
static inline struct vcpu *unit2vcpu_cpu(const struct sched_unit *unit,
@@ -2532,36 +2522,22 @@ void __init scheduler_init(void)
}
/*
- * Move a pCPU outside of the influence of the scheduler of its current
- * cpupool, or subject it to the scheduler of a new cpupool.
- *
- * For the pCPUs that are removed from their cpupool, their scheduler becomes
- * &sched_idle_ops (the idle scheduler).
+ * Move a pCPU from free cpus (running the idle scheduler) to a cpupool
+ * using any "real" scheduler.
+ * The cpu is still marked as "free" and not yet valid for its cpupool.
*/
-int schedule_cpu_switch(unsigned int cpu, struct cpupool *c)
+int schedule_cpu_add(unsigned int cpu, struct cpupool *c)
{
struct vcpu *idle;
- void *ppriv, *ppriv_old, *vpriv, *vpriv_old;
- struct scheduler *old_ops = get_sched_res(cpu)->scheduler;
- struct scheduler *new_ops = (c == NULL) ? &sched_idle_ops : c->sched;
- struct sched_resource *sd = get_sched_res(cpu);
- struct cpupool *old_pool = sd->cpupool;
+ void *ppriv, *vpriv;
+ struct scheduler *new_ops = c->sched;
+ struct sched_resource *sr = get_sched_res(cpu);
spinlock_t *old_lock, *new_lock;
unsigned long flags;
- /*
- * pCPUs only move from a valid cpupool to free (i.e., out of any pool),
- * or from free to a valid cpupool. In the former case (which happens when
- * c is NULL), we want the CPU to have been marked as free already, as
- * well as to not be valid for the source pool any longer, when we get to
- * here. In the latter case (which happens when c is a valid cpupool), we
- * want the CPU to still be marked as free, as well as to not yet be valid
- * for the destination pool.
- */
- ASSERT(c != old_pool && (c != NULL || old_pool != NULL));
ASSERT(cpumask_test_cpu(cpu, &cpupool_free_cpus));
- ASSERT((c == NULL && !cpumask_test_cpu(cpu, old_pool->cpu_valid)) ||
- (c != NULL && !cpumask_test_cpu(cpu, c->cpu_valid)));
+ ASSERT(!cpumask_test_cpu(cpu, c->cpu_valid));
+ ASSERT(get_sched_res(cpu)->cpupool == NULL);
/*
* To setup the cpu for the new scheduler we need:
@@ -2586,52 +2562,91 @@ int schedule_cpu_switch(unsigned int cpu, struct
cpupool *c)
return -ENOMEM;
}
- sched_do_tick_suspend(old_ops, cpu);
-
/*
- * The actual switch, including (if necessary) the rerouting of the
- * scheduler lock to whatever new_ops prefers, needs to happen in one
- * critical section, protected by old_ops' lock, or races are possible.
- * It is, in fact, the lock of another scheduler that we are taking (the
- * scheduler of the cpupool that cpu still belongs to). But that is ok
- * as, anyone trying to schedule on this cpu will spin until when we
- * release that lock (bottom of this function). When he'll get the lock
- * --thanks to the loop inside *_schedule_lock() functions-- he'll notice
- * that the lock itself changed, and retry acquiring the new one (which
- * will be the correct, remapped one, at that point).
+ * The actual switch, including the rerouting of the scheduler lock to
+ * whatever new_ops prefers, needs to happen in one critical section,
+ * protected by old_ops' lock, or races are possible.
+ * It is, in fact, the lock of the idle scheduler that we are taking.
+ * But that is ok as anyone trying to schedule on this cpu will spin until
+ * when we release that lock (bottom of this function). When he'll get the
+ * lock --thanks to the loop inside *_schedule_lock() functions-- he'll
+ * notice that the lock itself changed, and retry acquiring the new one
+ * (which will be the correct, remapped one, at that point).
*/
old_lock = pcpu_schedule_lock_irqsave(cpu, &flags);
- vpriv_old = idle->sched_unit->priv;
- ppriv_old = sd->sched_priv;
new_lock = sched_switch_sched(new_ops, cpu, ppriv, vpriv);
- sd->scheduler = new_ops;
- sd->sched_priv = ppriv;
+ sr->scheduler = new_ops;
+ sr->sched_priv = ppriv;
/*
- * The data above is protected under new_lock, which may be unlocked.
- * Another CPU can take new_lock as soon as sd->schedule_lock is visible,
- * and must observe all prior initialisation.
+ * Reroute the lock to the per pCPU lock as /last/ thing. In fact,
+ * if it is free (and it can be) we want that anyone that manages
+ * taking it, finds all the initializations we've done above in place.
*/
smp_wmb();
- sd->schedule_lock = new_lock;
+ sr->schedule_lock = new_lock;
- /* _Not_ pcpu_schedule_unlock(): schedule_lock may have changed! */
+ /* _Not_ pcpu_schedule_unlock(): schedule_lock has changed! */
spin_unlock_irqrestore(old_lock, flags);
sched_do_tick_resume(new_ops, cpu);
+ sr->granularity = cpupool_get_granularity(c);
+ sr->cpupool = c;
+ /* The cpu is added to a pool, trigger it to go pick up some work */
+ cpu_raise_softirq(cpu, SCHEDULE_SOFTIRQ);
+
+ return 0;
+}
+
+/*
+ * Remove a pCPU from its cpupool. Its scheduler becomes &sched_idle_ops
+ * (the idle scheduler).
+ * The cpu is already marked as "free" and not valid any longer for its
+ * cpupool.
+ */
+int schedule_cpu_rm(unsigned int cpu)
+{
+ struct vcpu *idle;
+ void *ppriv_old, *vpriv_old;
+ struct sched_resource *sr = get_sched_res(cpu);
+ struct scheduler *old_ops = sr->scheduler;
+ spinlock_t *old_lock;
+ unsigned long flags;
+
+ ASSERT(sr->cpupool != NULL);
+ ASSERT(cpumask_test_cpu(cpu, &cpupool_free_cpus));
+ ASSERT(!cpumask_test_cpu(cpu, sr->cpupool->cpu_valid));
+
+ idle = idle_vcpu[cpu];
+
+ sched_do_tick_suspend(old_ops, cpu);
+
+ /* See comment in schedule_cpu_add() regarding lock switching. */
+ old_lock = pcpu_schedule_lock_irqsave(cpu, &flags);
+
+ vpriv_old = idle->sched_unit->priv;
+ ppriv_old = sr->sched_priv;
+
+ idle->sched_unit->priv = NULL;
+ sr->scheduler = &sched_idle_ops;
+ sr->sched_priv = NULL;
+
+ smp_mb();
+ sr->schedule_lock = &sched_free_cpu_lock;
+
+ /* _Not_ pcpu_schedule_unlock(): schedule_lock may have changed! */
+ spin_unlock_irqrestore(old_lock, flags);
+
sched_deinit_pdata(old_ops, ppriv_old, cpu);
sched_free_udata(old_ops, vpriv_old);
sched_free_pdata(old_ops, ppriv_old, cpu);
- get_sched_res(cpu)->granularity = cpupool_get_granularity(c);
- get_sched_res(cpu)->cpupool = c;
- /* When a cpu is added to a pool, trigger it to go pick up some work */
- if ( c != NULL )
- cpu_raise_softirq(cpu, SCHEDULE_SOFTIRQ);
+ sr->granularity = 1;
+ sr->cpupool = NULL;
return 0;
}
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index aa8257edc9..a40bd5fb56 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -920,7 +920,8 @@ struct scheduler;
struct scheduler *scheduler_get_default(void);
struct scheduler *scheduler_alloc(unsigned int sched_id, int *perr);
void scheduler_free(struct scheduler *sched);
-int schedule_cpu_switch(unsigned int cpu, struct cpupool *c);
+int schedule_cpu_add(unsigned int cpu, struct cpupool *c);
+int schedule_cpu_rm(unsigned int cpu);
void vcpu_set_periodic_timer(struct vcpu *v, s_time_t value);
int cpu_disable_scheduler(unsigned int cpu);
void sched_setup_dom0_vcpus(struct domain *d);
--
2.16.4
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