Re: [PATCH 6 of 6 v2] xen: sched_credit: add some tracing

[George Dunlap <george.dunlap@eu.citrix.com>]

On 12/12/12 02:52, Dario Faggioli wrote:
> About tickling, and PCPU selection.
>
> Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
> ---
> Changes from v1:
>   * Dummy `struct d {}', accommodating `cpu' only, removed
>     in spite of the much more readable `trace_var(..., sizeof(cpu), &cpu)',
>     as suggested.
>
> diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
> --- a/xen/common/sched_credit.c
> +++ b/xen/common/sched_credit.c
> @@ -21,6 +21,7 @@
>   #include <asm/atomic.h>
>   #include <xen/errno.h>
>   #include <xen/keyhandler.h>
> +#include <xen/trace.h>
>   
>   
>   /*
> @@ -97,6 +98,18 @@
>   
>   
>   /*
> + * Credit tracing events ("only" 512 available!). Check
> + * include/public/trace.h for more details.
> + */
> +#define TRC_CSCHED_SCHED_TASKLET TRC_SCHED_CLASS_EVT(CSCHED, 1)
> +#define TRC_CSCHED_ACCOUNT_START TRC_SCHED_CLASS_EVT(CSCHED, 2)
> +#define TRC_CSCHED_ACCOUNT_STOP  TRC_SCHED_CLASS_EVT(CSCHED, 3)
> +#define TRC_CSCHED_STOLEN_VCPU   TRC_SCHED_CLASS_EVT(CSCHED, 4)
> +#define TRC_CSCHED_PICKED_CPU    TRC_SCHED_CLASS_EVT(CSCHED, 5)
> +#define TRC_CSCHED_TICKLE        TRC_SCHED_CLASS_EVT(CSCHED, 6)
> +
> +
> +/*
>    * Boot parameters
>    */
>   static int __read_mostly sched_credit_tslice_ms = CSCHED_DEFAULT_TSLICE_MS;
> @@ -315,9 +328,18 @@ static inline void
>           }
>       }
>   
> -    /* Send scheduler interrupts to designated CPUs */
>       if ( !cpumask_empty(&mask) )
> +    {
> +        if ( unlikely(tb_init_done) )
> +        {
> +            /* Avoid TRACE_*: saves checking !tb_init_done each step */
> +            for_each_cpu(cpu, &mask)
> +                trace_var(TRC_CSCHED_TICKLE, 0, sizeof(cpu), &cpu);
> +        }

Hmm, probably should have pointed this out before, but trace_var() is a 
static inline which checks tb_init_done -- you want __trace_var(). :-)

The rest still looks good.

  -George

> +
> +        /* Send scheduler interrupts to designated CPUs */
>           cpumask_raise_softirq(&mask, SCHEDULE_SOFTIRQ);
> +    }
>   }
>   
>   static void
> @@ -554,6 +576,8 @@ static int
>       if ( commit && spc )
>          spc->idle_bias = cpu;
>   
> +    TRACE_3D(TRC_CSCHED_PICKED_CPU, vc->domain->domain_id, vc->vcpu_id, cpu);
> +
>       return cpu;
>   }
>   
> @@ -586,6 +610,9 @@ static inline void
>           }
>       }
>   
> +    TRACE_3D(TRC_CSCHED_ACCOUNT_START, sdom->dom->domain_id,
> +             svc->vcpu->vcpu_id, sdom->active_vcpu_count);
> +
>       spin_unlock_irqrestore(&prv->lock, flags);
>   }
>   
> @@ -608,6 +635,9 @@ static inline void
>       {
>           list_del_init(&sdom->active_sdom_elem);
>       }
> +
> +    TRACE_3D(TRC_CSCHED_ACCOUNT_STOP, sdom->dom->domain_id,
> +             svc->vcpu->vcpu_id, sdom->active_vcpu_count);
>   }
>   
>   static void
> @@ -1241,6 +1271,8 @@ csched_runq_steal(int peer_cpu, int cpu,
>               if (__csched_vcpu_is_migrateable(vc, cpu))
>               {
>                   /* We got a candidate. Grab it! */
> +                TRACE_3D(TRC_CSCHED_STOLEN_VCPU, peer_cpu,
> +                         vc->domain->domain_id, vc->vcpu_id);
>                   SCHED_VCPU_STAT_CRANK(speer, migrate_q);
>                   SCHED_STAT_CRANK(migrate_queued);
>                   WARN_ON(vc->is_urgent);
> @@ -1401,6 +1433,7 @@ csched_schedule(
>       /* Tasklet work (which runs in idle VCPU context) overrides all else. */
>       if ( tasklet_work_scheduled )
>       {
> +        TRACE_0D(TRC_CSCHED_SCHED_TASKLET);
>           snext = CSCHED_VCPU(idle_vcpu[cpu]);
>           snext->pri = CSCHED_PRI_TS_BOOST;
>       }