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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 1/4] xen: sched: introduce 'adjust_affinity' hook.
For now, just as a way to give a scheduler an "heads up",
about the fact that the affinity changed.
This enables some optimizations, such as pre-computing
and storing (e.g., in flags) facts like a vcpu being
exclusively pinned to a pcpu, or having or not a
soft affinity. I.e., conditions that, despite the fact
that they rarely change, are right now checked very
frequently, even in hot paths.
Note also that this, in future, may turn out as a useful
mean for, e.g., having the schedulers vet, ack or nack
the changes themselves.
Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
---
Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
Cc: Anshul Makkar <anshulmakkar@xxxxxxxxx>
---
xen/arch/x86/dom0_build.c | 4 +--
xen/common/schedule.c | 62 +++++++++++++++++++++++++++++++++-----------
xen/include/xen/sched-if.h | 3 ++
xen/include/xen/sched.h | 3 ++
4 files changed, 55 insertions(+), 17 deletions(-)
diff --git a/xen/arch/x86/dom0_build.c b/xen/arch/x86/dom0_build.c
index f616b99..94e4b7f 100644
--- a/xen/arch/x86/dom0_build.c
+++ b/xen/arch/x86/dom0_build.c
@@ -125,8 +125,8 @@ struct vcpu *__init dom0_setup_vcpu(struct domain *d,
if ( v )
{
if ( !d->is_pinned && !dom0_affinity_relaxed )
- cpumask_copy(v->cpu_hard_affinity, &dom0_cpus);
- cpumask_copy(v->cpu_soft_affinity, &dom0_cpus);
+ sched_set_affinity(v, &dom0_cpus, NULL);
+ sched_set_affinity(v, NULL, &dom0_cpus);
}
return v;
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 8827921..a8b82fd 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -256,6 +256,9 @@ static void sched_spin_unlock_double(spinlock_t *lock1,
spinlock_t *lock2,
int sched_init_vcpu(struct vcpu *v, unsigned int processor)
{
struct domain *d = v->domain;
+ cpumask_t allcpus;
+
+ cpumask_setall(&allcpus);
/*
* Initialize processor and affinity settings. The idler, and potentially
@@ -263,11 +266,9 @@ int sched_init_vcpu(struct vcpu *v, unsigned int processor)
*/
v->processor = processor;
if ( is_idle_domain(d) || d->is_pinned )
- cpumask_copy(v->cpu_hard_affinity, cpumask_of(processor));
+ sched_set_affinity(v, cpumask_of(processor), &allcpus);
else
- cpumask_setall(v->cpu_hard_affinity);
-
- cpumask_setall(v->cpu_soft_affinity);
+ sched_set_affinity(v, &allcpus, &allcpus);
/* Initialise the per-vcpu timers. */
init_timer(&v->periodic_timer, vcpu_periodic_timer_fn,
@@ -359,6 +360,7 @@ int sched_move_domain(struct domain *d, struct cpupool *c)
for_each_vcpu ( d, v )
{
spinlock_t *lock;
+ cpumask_t allcpus;
vcpudata = v->sched_priv;
@@ -366,10 +368,12 @@ int sched_move_domain(struct domain *d, struct cpupool *c)
migrate_timer(&v->singleshot_timer, new_p);
migrate_timer(&v->poll_timer, new_p);
- cpumask_setall(v->cpu_hard_affinity);
- cpumask_setall(v->cpu_soft_affinity);
+ cpumask_setall(&allcpus);
lock = vcpu_schedule_lock_irq(v);
+
+ sched_set_affinity(v, &allcpus, &allcpus);
+
v->processor = new_p;
/*
* With v->processor modified we must not
@@ -680,7 +684,7 @@ void restore_vcpu_affinity(struct domain *d)
if ( v->affinity_broken )
{
- cpumask_copy(v->cpu_hard_affinity, v->cpu_hard_affinity_saved);
+ sched_set_affinity(v, v->cpu_hard_affinity_saved, NULL);
v->affinity_broken = 0;
}
@@ -744,6 +748,8 @@ int cpu_disable_scheduler(unsigned int cpu)
if ( cpumask_empty(&online_affinity) &&
cpumask_test_cpu(cpu, v->cpu_hard_affinity) )
{
+ cpumask_t allcpus;
+
if ( v->affinity_broken )
{
/* The vcpu is temporarily pinned, can't move it. */
@@ -761,7 +767,8 @@ int cpu_disable_scheduler(unsigned int cpu)
else
printk(XENLOG_DEBUG "Breaking affinity for %pv\n", v);
- cpumask_setall(v->cpu_hard_affinity);
+ cpumask_setall(&allcpus);
+ sched_set_affinity(v, &allcpus, NULL);
}
if ( v->processor != cpu )
@@ -831,8 +838,26 @@ int cpu_disable_scheduler(unsigned int cpu)
return ret;
}
+/*
+ * In general, this must be called with the scheduler lock held, because the
+ * adjust_affinity hook may want to modify the vCPU state. However, when the
+ * vCPU is being initialized (either for dom0 or domU) there is no risk of
+ * races, and it's fine to not take the look (we're talking about
+ * dom0_setup_vcpu() an sched_init_vcpu()).
+ */
+void sched_set_affinity(
+ struct vcpu *v, const cpumask_t *hard, const cpumask_t *soft)
+{
+ SCHED_OP(dom_scheduler(v->domain), adjust_affinity, v, hard, soft);
+
+ if ( hard )
+ cpumask_copy(v->cpu_hard_affinity, hard);
+ if ( soft )
+ cpumask_copy(v->cpu_hard_affinity, soft);
+}
+
static int vcpu_set_affinity(
- struct vcpu *v, const cpumask_t *affinity, cpumask_t *which)
+ struct vcpu *v, const cpumask_t *affinity, const cpumask_t *which)
{
spinlock_t *lock;
int ret = 0;
@@ -843,12 +868,19 @@ static int vcpu_set_affinity(
ret = -EBUSY;
else
{
- cpumask_copy(which, affinity);
-
/*
- * Always ask the scheduler to re-evaluate placement
- * when changing the affinity.
+ * Tell the scheduler we changes something about affinity,
+ * and ask to re-evaluate vcpu placement.
*/
+ if ( which == v->cpu_hard_affinity )
+ {
+ sched_set_affinity(v, affinity, NULL);
+ }
+ else
+ {
+ ASSERT(which == v->cpu_soft_affinity);
+ sched_set_affinity(v, NULL, affinity);
+ }
set_bit(_VPF_migrating, &v->pause_flags);
}
@@ -1086,7 +1118,7 @@ int vcpu_pin_override(struct vcpu *v, int cpu)
{
if ( v->affinity_broken )
{
- cpumask_copy(v->cpu_hard_affinity, v->cpu_hard_affinity_saved);
+ sched_set_affinity(v, v->cpu_hard_affinity_saved, NULL);
v->affinity_broken = 0;
set_bit(_VPF_migrating, &v->pause_flags);
ret = 0;
@@ -1100,7 +1132,7 @@ int vcpu_pin_override(struct vcpu *v, int cpu)
{
cpumask_copy(v->cpu_hard_affinity_saved, v->cpu_hard_affinity);
v->affinity_broken = 1;
- cpumask_copy(v->cpu_hard_affinity, cpumask_of(cpu));
+ sched_set_affinity(v, cpumask_of(cpu), NULL);
set_bit(_VPF_migrating, &v->pause_flags);
ret = 0;
}
diff --git a/xen/include/xen/sched-if.h b/xen/include/xen/sched-if.h
index c4a4935..982c780 100644
--- a/xen/include/xen/sched-if.h
+++ b/xen/include/xen/sched-if.h
@@ -172,6 +172,9 @@ struct scheduler {
unsigned int);
int (*adjust) (const struct scheduler *, struct domain *,
struct xen_domctl_scheduler_op *);
+ void (*adjust_affinity)(const struct scheduler *, struct vcpu *,
+ const struct cpumask *,
+ const struct cpumask *);
int (*adjust_global) (const struct scheduler *,
struct xen_sysctl_scheduler_op *);
void (*dump_settings) (const struct scheduler *);
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index b03afb4..4f386f1 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -840,6 +840,9 @@ void scheduler_free(struct scheduler *sched);
int schedule_cpu_switch(unsigned int cpu, struct cpupool *c);
void vcpu_force_reschedule(struct vcpu *v);
int cpu_disable_scheduler(unsigned int cpu);
+/* We need it in dom0_setup_vcpu */
+void sched_set_affinity(struct vcpu *v, const cpumask_t *hard,
+ const cpumask_t *soft);
int vcpu_set_hard_affinity(struct vcpu *v, const cpumask_t *affinity);
int vcpu_set_soft_affinity(struct vcpu *v, const cpumask_t *affinity);
void restore_vcpu_affinity(struct domain *d);
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