[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 4/5] xen: sched_null: support for hard affinity
As a (rudimental) way of directing and affecting the placement logic implemented by the scheduler, support vCPU hard affinity. Basically, a vCPU will now be assigned only to a pCPU that is part of its own hard affinity. If such pCPU(s) is (are) busy, the vCPU will wait, like it happens when there are no free pCPUs. Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx> --- Cc: George Dunlap <george.dunlap@xxxxxxxxxx> Cc: Stefano Stabellini <stefano@xxxxxxxxxxx> Cc: Julien Grall <julien.grall@xxxxxxx> Cc: Jonathan Davies <Jonathan.Davies@xxxxxxxxxx> Cc: Marcus Granado <marcus.granado@xxxxxxxxxx> --- Changes from v1: - coding style fixes (removed some hard tabs); - better signature for check_nvc_affinity() (also renamed in vcpu_check_affinity()); - fixed bug in null_vcpu_remove() using uninitialized cpumask. --- xen/common/sched_null.c | 50 ++++++++++++++++++++++++++++++++--------------- 1 file changed, 34 insertions(+), 16 deletions(-) diff --git a/xen/common/sched_null.c b/xen/common/sched_null.c index c2c4182..96652a0 100644 --- a/xen/common/sched_null.c +++ b/xen/common/sched_null.c @@ -115,6 +115,14 @@ static inline struct null_dom *null_dom(const struct domain *d) return d->sched_priv; } +static inline bool vcpu_check_affinity(struct vcpu *v, unsigned int cpu) +{ + cpumask_and(cpumask_scratch_cpu(cpu), v->cpu_hard_affinity, + cpupool_domain_cpumask(v->domain)); + + return cpumask_test_cpu(cpu, cpumask_scratch_cpu(cpu)); +} + static int null_init(struct scheduler *ops) { struct null_private *prv; @@ -276,16 +284,22 @@ static unsigned int pick_cpu(struct null_private *prv, struct vcpu *v) ASSERT(spin_is_locked(per_cpu(schedule_data, cpu).schedule_lock)); + cpumask_and(cpumask_scratch_cpu(cpu), v->cpu_hard_affinity, cpus); + /* - * If our processor is free, or we are assigned to it, and it is - * also still valid, just go for it. + * If our processor is free, or we are assigned to it, and it is also + * still valid and part of our affinity, just go for it. + * (Note that we may call vcpu_check_affinity(), but we deliberately + * don't, so we get to keep in the scratch cpumask what we have just + * put in it.) */ if ( likely((per_cpu(npc, cpu).vcpu == NULL || per_cpu(npc, cpu).vcpu == v) - && cpumask_test_cpu(cpu, cpus)) ) + && cpumask_test_cpu(cpu, cpumask_scratch_cpu(cpu))) ) return cpu; - /* If not, just go for a valid free pCPU, if any */ - cpumask_and(cpumask_scratch_cpu(cpu), &prv->cpus_free, cpus); + /* If not, just go for a free pCPU, within our affinity, if any */ + cpumask_and(cpumask_scratch_cpu(cpu), cpumask_scratch_cpu(cpu), + &prv->cpus_free); new_cpu = cpumask_first(cpumask_scratch_cpu(cpu)); if ( likely(new_cpu != nr_cpu_ids) ) @@ -302,7 +316,8 @@ static unsigned int pick_cpu(struct null_private *prv, struct vcpu *v) * as we will actually assign the vCPU to the pCPU we return from here, * only if the pCPU is free. */ - return cpumask_any(cpus); + cpumask_and(cpumask_scratch_cpu(cpu), cpus, v->cpu_hard_affinity); + return cpumask_any(cpumask_scratch_cpu(cpu)); } static void vcpu_assign(struct null_private *prv, struct vcpu *v, @@ -361,6 +376,7 @@ static void null_vcpu_insert(const struct scheduler *ops, struct vcpu *v) { struct null_private *prv = null_priv(ops); struct null_vcpu *nvc = null_vcpu(v); + unsigned int cpu; spinlock_t *lock; ASSERT(!is_idle_vcpu(v)); @@ -368,23 +384,25 @@ static void null_vcpu_insert(const struct scheduler *ops, struct vcpu *v) lock = vcpu_schedule_lock_irq(v); retry: - v->processor = pick_cpu(prv, v); + cpu = v->processor = pick_cpu(prv, v); spin_unlock(lock); lock = vcpu_schedule_lock(v); + cpumask_and(cpumask_scratch_cpu(cpu), v->cpu_hard_affinity, + cpupool_domain_cpumask(v->domain)); + /* If the pCPU is free, we assign v to it */ - if ( likely(per_cpu(npc, v->processor).vcpu == NULL) ) + if ( likely(per_cpu(npc, cpu).vcpu == NULL) ) { /* * Insert is followed by vcpu_wake(), so there's no need to poke * the pcpu with the SCHEDULE_SOFTIRQ, as wake will do that. */ - vcpu_assign(prv, v, v->processor); + vcpu_assign(prv, v, cpu); } - else if ( cpumask_intersects(&prv->cpus_free, - cpupool_domain_cpumask(v->domain)) ) + else if ( cpumask_intersects(&prv->cpus_free, cpumask_scratch_cpu(cpu)) ) { /* * If the pCPU is not free (e.g., because we raced with another @@ -413,7 +431,6 @@ static void null_vcpu_insert(const struct scheduler *ops, struct vcpu *v) static void _vcpu_remove(struct null_private *prv, struct vcpu *v) { unsigned int cpu = v->processor; - struct domain *d = v->domain; struct null_vcpu *wvc; ASSERT(list_empty(&null_vcpu(v)->waitq_elem)); @@ -425,7 +442,7 @@ static void _vcpu_remove(struct null_private *prv, struct vcpu *v) * If yes, we assign it to cpu, in spite of v. */ wvc = list_first_entry_or_null(&prv->waitq, struct null_vcpu, waitq_elem); - if ( wvc && cpumask_test_cpu(cpu, cpupool_domain_cpumask(d)) ) + if ( wvc && vcpu_check_affinity(wvc->vcpu, cpu) ) { list_del_init(&wvc->waitq_elem); vcpu_assign(prv, wvc->vcpu, cpu); @@ -547,11 +564,12 @@ static void null_vcpu_migrate(const struct scheduler *ops, struct vcpu *v, * Let's now consider new_cpu, which is where v is being sent. It can be * either free, or have a vCPU already assigned to it. * - * In the former case, we should assign v to it, and try to get it to run. + * In the former case, we should assign v to it, and try to get it to run, + * if possible, according to affinity. * * In latter, all we can do is to park v in the waitqueue. */ - if ( per_cpu(npc, new_cpu).vcpu == NULL ) + if ( per_cpu(npc, new_cpu).vcpu == NULL && vcpu_check_affinity(v, new_cpu) ) { /* v might have been in the waitqueue, so remove it */ spin_lock(&prv->waitq_lock); @@ -635,7 +653,7 @@ static struct task_slice null_schedule(const struct scheduler *ops, { spin_lock(&prv->waitq_lock); wvc = list_first_entry_or_null(&prv->waitq, struct null_vcpu, waitq_elem); - if ( wvc ) + if ( wvc && vcpu_check_affinity(wvc->vcpu, cpu) ) { vcpu_assign(prv, wvc->vcpu, cpu); list_del_init(&wvc->waitq_elem); _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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