Re: [Xen-devel] [PATCH 2/6] xen: credit2: make the cpu to runqueue map per-cpu

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 06/23/2017 11:54 AM, Dario Faggioli wrote:
> Instead of keeping an NR_CPUS big array of int-s,
> directly inside csched2_private, use a per-cpu
> variable.
> 
> That's especially beneficial (in terms of saved
> memory) when there are more instance of Credit2 (in
> different cpupools), and also helps fitting
> csched2_private itself into CPU caches.
> 
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

Sounds good:

Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>

> ---
> Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
> Cc: Anshul Makkar <anshulmakkar@xxxxxxxxx>
> ---
>  xen/common/sched_credit2.c |   33 ++++++++++++++++++++-------------
>  1 file changed, 20 insertions(+), 13 deletions(-)
> 
> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
> index 10d9488..15862f2 100644
> --- a/xen/common/sched_credit2.c
> +++ b/xen/common/sched_credit2.c
> @@ -383,7 +383,6 @@ struct csched2_private {
>      
>      struct list_head sdom; /* Used mostly for dump keyhandler. */
>  
> -    int runq_map[NR_CPUS];
>      cpumask_t active_queues; /* Queues which may have active cpus */
>      struct csched2_runqueue_data *rqd;
>  
> @@ -393,6 +392,14 @@ struct csched2_private {
>  };
>  
>  /*
> + * Physical CPU
> + *
> + * The only per-pCPU information we need to maintain is of which runqueue
> + * each CPU is part of.
> + */
> +static DEFINE_PER_CPU(int, runq_map);
> +
> +/*
>   * Virtual CPU
>   */
>  struct csched2_vcpu {
> @@ -448,16 +455,16 @@ static inline struct csched2_dom *csched2_dom(const 
> struct domain *d)
>  }
>  
>  /* CPU to runq_id macro */
> -static inline int c2r(const struct scheduler *ops, unsigned int cpu)
> +static inline int c2r(unsigned int cpu)
>  {
> -    return csched2_priv(ops)->runq_map[(cpu)];
> +    return per_cpu(runq_map, cpu);
>  }
>  
>  /* CPU to runqueue struct macro */
>  static inline struct csched2_runqueue_data *c2rqd(const struct scheduler 
> *ops,
>                                                    unsigned int cpu)
>  {
> -    return &csched2_priv(ops)->rqd[c2r(ops, cpu)];
> +    return &csched2_priv(ops)->rqd[c2r(cpu)];
>  }
>  
>  /*
> @@ -1082,7 +1089,7 @@ runq_insert(const struct scheduler *ops, struct 
> csched2_vcpu *svc)
>      ASSERT(spin_is_locked(per_cpu(schedule_data, cpu).schedule_lock));
>  
>      ASSERT(!vcpu_on_runq(svc));
> -    ASSERT(c2r(ops, cpu) == c2r(ops, svc->vcpu->processor));
> +    ASSERT(c2r(cpu) == c2r(svc->vcpu->processor));
>  
>      ASSERT(&svc->rqd->runq == runq);
>      ASSERT(!is_idle_vcpu(svc->vcpu));
> @@ -1733,7 +1740,7 @@ csched2_cpu_pick(const struct scheduler *ops, struct 
> vcpu *vc)
>      if ( min_rqi == -1 )
>      {
>          new_cpu = get_fallback_cpu(svc);
> -        min_rqi = c2r(ops, new_cpu);
> +        min_rqi = c2r(new_cpu);
>          min_avgload = prv->rqd[min_rqi].b_avgload;
>          goto out_up;
>      }
> @@ -2622,7 +2629,7 @@ csched2_schedule(
>              unsigned tasklet:8, idle:8, smt_idle:8, tickled:8;
>          } d;
>          d.cpu = cpu;
> -        d.rq_id = c2r(ops, cpu);
> +        d.rq_id = c2r(cpu);
>          d.tasklet = tasklet_work_scheduled;
>          d.idle = is_idle_vcpu(current);
>          d.smt_idle = cpumask_test_cpu(cpu, &rqd->smt_idle);
> @@ -2783,7 +2790,7 @@ dump_pcpu(const struct scheduler *ops, int cpu)
>  #define cpustr keyhandler_scratch
>  
>      cpumask_scnprintf(cpustr, sizeof(cpustr), per_cpu(cpu_sibling_mask, 
> cpu));
> -    printk("CPU[%02d] runq=%d, sibling=%s, ", cpu, c2r(ops, cpu), cpustr);
> +    printk("CPU[%02d] runq=%d, sibling=%s, ", cpu, c2r(cpu), cpustr);
>      cpumask_scnprintf(cpustr, sizeof(cpustr), per_cpu(cpu_core_mask, cpu));
>      printk("core=%s\n", cpustr);
>  
> @@ -2930,7 +2937,7 @@ init_pdata(struct csched2_private *prv, unsigned int 
> cpu)
>      }
>      
>      /* Set the runqueue map */
> -    prv->runq_map[cpu] = rqi;
> +    per_cpu(runq_map, cpu) = rqi;
>      
>      __cpumask_set_cpu(cpu, &rqd->idle);
>      __cpumask_set_cpu(cpu, &rqd->active);
> @@ -3034,7 +3041,7 @@ csched2_deinit_pdata(const struct scheduler *ops, void 
> *pcpu, int cpu)
>      ASSERT(!pcpu && cpumask_test_cpu(cpu, &prv->initialized));
>      
>      /* Find the old runqueue and remove this cpu from it */
> -    rqi = prv->runq_map[cpu];
> +    rqi = per_cpu(runq_map, cpu);
>  
>      rqd = prv->rqd + rqi;
>  
> @@ -3055,6 +3062,8 @@ csched2_deinit_pdata(const struct scheduler *ops, void 
> *pcpu, int cpu)
>      else if ( rqd->pick_bias == cpu )
>          rqd->pick_bias = cpumask_first(&rqd->active);
>  
> +    per_cpu(runq_map, cpu) = -1;
> +
>      spin_unlock(&rqd->lock);
>  
>      __cpumask_clear_cpu(cpu, &prv->initialized);
> @@ -3121,10 +3130,8 @@ csched2_init(struct scheduler *ops)
>          return -ENOMEM;
>      }
>      for ( i = 0; i < nr_cpu_ids; i++ )
> -    {
> -        prv->runq_map[i] = -1;
>          prv->rqd[i].id = -1;
> -    }
> +
>      /* initialize ratelimit */
>      prv->ratelimit_us = sched_ratelimit_us;
>  
> 


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