Re: [Xen-devel] [PATCH 05/14] xen: RTDS: pack trace data better for xentrace_format

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Feb 05, 2016 at 07:34:05PM +0100, Dario Faggioli wrote:
> when tracing runstate changes, the vcpu and domain IDs
> are encoded in the lower and higher, respectively, parts
> of a 32 bits integer. When decoding a trace with
> xentrace_format, this makes it possible to display
> such events like this:
> 
> CPU0  833435853624 (+     768)  running_to_runnable [ dom:vcpu = 0x7fff0000 ]
> CPU0  833435854416 (+     792)  runnable_to_running [ dom:vcpu = 0x00000007 ]
> 
> For consistency, we should do the same when displaying
> the events coming from the RTDS scheduler (when using
> the same tool), and to do that, we need to invert the
> order in which the fields are being put in the trace
> struct right now.
> 
> While there, we also:
>  - fix the use of TRC_RTDS_SCHED_TASKLET (it should
>    only be involved when a tasklet is scheduled, not
>    _every_ time rt_schedule() is invoked!);
>  - remove a very chatty and useless (nothing has been
>    picked!) use of TRC_RTDS_RUNQ_PICK.
> 

I would add: "One can observe the case where nothing has been
picked by looking at when the cpu_idle is invoked - which is
the same mechanism on credit1,2 where we can see if the
scheduler hadn't picked anything from the runqueue."


Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> ---
> Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
> Cc: Meng Xu <xumengpanda@xxxxxxxxx>
> Cc: Tianyang Chen <tiche@xxxxxxxxxxxxxx>
> Cc: Olaf Hering <olaf@xxxxxxxxx>
> ---
>  xen/common/sched_rt.c |   27 ++++-----------------------
>  1 file changed, 4 insertions(+), 23 deletions(-)
> 
> diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
> index 2e5430f..53de6d6 100644
> --- a/xen/common/sched_rt.c
> +++ b/xen/common/sched_rt.c
> @@ -362,7 +362,7 @@ rt_update_deadline(s_time_t now, struct rt_vcpu *svc)
>      /* TRACE */
>      {
>          struct {
> -            unsigned dom:16,vcpu:16;
> +            unsigned vcpu:16, dom:16;
>              unsigned cur_deadline_lo, cur_deadline_hi;
>              unsigned cur_budget_lo, cur_budget_hi;
>          } d;
> @@ -711,7 +711,7 @@ burn_budget(const struct scheduler *ops, struct rt_vcpu 
> *svc, s_time_t now)
>      /* TRACE */
>      {
>          struct {
> -            unsigned dom:16, vcpu:16;
> +            unsigned vcpu:16, dom:16;
>              unsigned cur_budget_lo;
>              unsigned cur_budget_hi;
>              int delta;
> @@ -763,7 +763,7 @@ __runq_pick(const struct scheduler *ops, const cpumask_t 
> *mask)
>          if( svc != NULL )
>          {
>              struct {
> -                unsigned dom:16, vcpu:16;
> +                unsigned vcpu:16, dom:16;
>                  unsigned cur_deadline_lo, cur_deadline_hi;
>                  unsigned cur_budget_lo, cur_budget_hi;
>              } d;
> @@ -777,8 +777,6 @@ __runq_pick(const struct scheduler *ops, const cpumask_t 
> *mask)
>                        sizeof(d),
>                        (unsigned char *) &d);
>          }
> -        else
> -            trace_var(TRC_RTDS_RUNQ_PICK, 1, 0, NULL);
>      }
>  
>      return svc;
> @@ -845,6 +843,7 @@ rt_schedule(const struct scheduler *ops, s_time_t now, 
> bool_t tasklet_work_sched
>  
>      if ( tasklet_work_scheduled )
>      {
> +        trace_var(TRC_RTDS_SCHED_TASKLET, 1, 0,  NULL);
>          snext = rt_vcpu(idle_vcpu[cpu]);
>      }
>      else
> @@ -885,24 +884,6 @@ rt_schedule(const struct scheduler *ops, s_time_t now, 
> bool_t tasklet_work_sched
>      ret.time = MIN(snext->budget, MAX_SCHEDULE); /* sched quantum */
>      ret.task = snext->vcpu;
>  
> -    /* TRACE */
> -    {
> -        struct {
> -            unsigned dom:16,vcpu:16;
> -            unsigned cur_deadline_lo, cur_deadline_hi;
> -            unsigned cur_budget_lo, cur_budget_hi;
> -        } d;
> -        d.dom = snext->vcpu->domain->domain_id;
> -        d.vcpu = snext->vcpu->vcpu_id;
> -        d.cur_deadline_lo = (unsigned) snext->cur_deadline;
> -        d.cur_deadline_hi = (unsigned) (snext->cur_deadline >> 32);
> -        d.cur_budget_lo = (unsigned) snext->cur_budget;
> -        d.cur_budget_hi = (unsigned) (snext->cur_budget >> 32);
> -        trace_var(TRC_RTDS_SCHED_TASKLET, 1,
> -                  sizeof(d),
> -                  (unsigned char *)&d);
> -    }
> -
>      return ret;
>  }
>  
> 
> 
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