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Re: [Xen-devel] [PATCH v2 09/10] xen/tools: tracing: trace (Credit2) runq traversal.



On Thu, Feb 9, 2017 at 1:59 PM, Dario Faggioli
<dario.faggioli@xxxxxxxxxx> wrote:
> When traversing a Credit2 runqueue to select the
> best candidate vCPU to be run next, show in the
> trace which vCPUs we consider.
>
> A bit verbose, but quite useful, considering that
> we may end up looking at, but then discarding, one
> of more vCPU. This will help understand which ones
> are skipped and why.

This sounds useful -- but what I don't quite understand is why it's
useful simply to know that a vcpu was considered, and not also know
specifically why it was decided against.  (I'm sure you've found it
useful or you wouldn't have submitted the patch.)

Anyway, I can check it in as-is (if it applies).

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

>
> Also, add how much credits the chosen vCPU has
> (in the TRC_CSCHED2_RUNQ_CANDIDATE record). And,
> while there, fix a bug in tools/xentrace/formats
> (still in the output of TRC_CSCHED2_RUNQ_CANDIDATE).
>
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> ---
> Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> ---
>  tools/xentrace/formats     |    3 ++-
>  tools/xentrace/xenalyze.c  |   15 +++++++++++++--
>  xen/common/sched_credit2.c |   15 +++++++++++++++
>  3 files changed, 30 insertions(+), 3 deletions(-)
>
> diff --git a/tools/xentrace/formats b/tools/xentrace/formats
> index db89f92..72c0b24 100644
> --- a/tools/xentrace/formats
> +++ b/tools/xentrace/formats
> @@ -65,9 +65,10 @@
>  0x00022210  CPU%(cpu)d  %(tsc)d (+%(reltsc)8d)  csched2:load_check     [ 
> lrq_id[16]:orq_id[16] = 0x%(1)08x, delta = %(2)d ]
>  0x00022211  CPU%(cpu)d  %(tsc)d (+%(reltsc)8d)  csched2:load_balance   [ 
> l_bavgload = 0x%(2)08x%(1)08x, o_bavgload = 0x%(4)08x%(3)08x, 
> lrq_id[16]:orq_id[16] = 0x%(5)08x ]
>  0x00022212  CPU%(cpu)d  %(tsc)d (+%(reltsc)8d)  csched2:pick_cpu       [ 
> b_avgload = 0x%(2)08x%(1)08x, dom:vcpu = 0x%(3)08x, rq_id[16]:new_cpu[16] = 
> %(4)d ]
> -0x00022213  CPU%(cpu)d  %(tsc)d (+%(reltsc)8d)  csched2:runq_candidate [ 
> dom:vcpu = 0x%(1)08x, skipped_vcpus = %(2)d tickled_cpu = %(3)d ]
> +0x00022213  CPU%(cpu)d  %(tsc)d (+%(reltsc)8d)  csched2:runq_candidate [ 
> dom:vcpu = 0x%(1)08x, credit = %(4)d, skipped_vcpus = %(3)d, tickled_cpu = 
> %(2)d ]
>  0x00022214  CPU%(cpu)d  %(tsc)d (+%(reltsc)8d)  csched2:schedule       [ 
> rq:cpu = 0x%(1)08x, tasklet[8]:idle[8]:smt_idle[8]:tickled[8] = %(2)08x ]
>  0x00022215  CPU%(cpu)d  %(tsc)d (+%(reltsc)8d)  csched2:ratelimit      [ 
> dom:vcpu = 0x%(1)08x, runtime = %(2)d ]
> +0x00022216  CPU%(cpu)d  %(tsc)d (+%(reltsc)8d)  csched2:runq_cand_chk  [ 
> dom:vcpu = 0x%(1)08x ]
>
>  0x00022801  CPU%(cpu)d  %(tsc)d (+%(reltsc)8d)  rtds:tickle        [ cpu = 
> %(1)d ]
>  0x00022802  CPU%(cpu)d  %(tsc)d (+%(reltsc)8d)  rtds:runq_pick     [ 
> dom:vcpu = 0x%(1)08x, cur_deadline = 0x%(3)08x%(2)08x, cur_budget = 
> 0x%(5)08x%(4)08x ]
> diff --git a/tools/xentrace/xenalyze.c b/tools/xentrace/xenalyze.c
> index a90da20..2678e2a 100644
> --- a/tools/xentrace/xenalyze.c
> +++ b/tools/xentrace/xenalyze.c
> @@ -7825,12 +7825,13 @@ void sched_process(struct pcpu_info *p)
>                  struct {
>                      unsigned vcpuid:16, domid:16;
>                      unsigned tickled_cpu, skipped;
> +                    int credit;
>                  } *r = (typeof(r))ri->d;
>
> -                printf(" %s csched2:runq_candidate d%uv%u, "
> +                printf(" %s csched2:runq_candidate d%uv%u, credit = %d, "
>                         "%u vcpus skipped, ",
>                         ri->dump_header, r->domid, r->vcpuid,
> -                       r->skipped);
> +                       r->credit, r->skipped);
>                  if (r->tickled_cpu == (unsigned)-1)
>                      printf("no cpu was tickled\n");
>                  else
> @@ -7864,6 +7865,16 @@ void sched_process(struct pcpu_info *p)
>                         r->runtime / 1000, r->runtime % 1000);
>              }
>              break;
> +        case TRC_SCHED_CLASS_EVT(CSCHED2, 23): /* RUNQ_CAND_CHECK  */
> +            if(opt.dump_all) {
> +                struct {
> +                    unsigned int vcpuid:16, domid:16;
> +                } *r = (typeof(r))ri->d;
> +
> +                printf(" %s csched2:runq_cand_check d%uv%u\n",
> +                       ri->dump_header, r->domid, r->vcpuid);
> +            }
> +            break;
>          /* RTDS (TRC_RTDS_xxx) */
>          case TRC_SCHED_CLASS_EVT(RTDS, 1): /* TICKLE           */
>              if(opt.dump_all) {
> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
> index 8057abf..35d6988 100644
> --- a/xen/common/sched_credit2.c
> +++ b/xen/common/sched_credit2.c
> @@ -57,6 +57,7 @@
>  #define TRC_CSCHED2_RUNQ_CANDIDATE   TRC_SCHED_CLASS_EVT(CSCHED2, 20)
>  #define TRC_CSCHED2_SCHEDULE         TRC_SCHED_CLASS_EVT(CSCHED2, 21)
>  #define TRC_CSCHED2_RATELIMIT        TRC_SCHED_CLASS_EVT(CSCHED2, 22)
> +#define TRC_CSCHED2_RUNQ_CAND_CHECK  TRC_SCHED_CLASS_EVT(CSCHED2, 23)
>
>  /*
>   * WARNING: This is still in an experimental phase.  Status and work can be 
> found at the
> @@ -2498,6 +2499,18 @@ runq_candidate(struct csched2_runqueue_data *rqd,
>      {
>          struct csched2_vcpu * svc = list_entry(iter, struct csched2_vcpu, 
> runq_elem);
>
> +        if ( unlikely(tb_init_done) )
> +        {
> +            struct {
> +                unsigned vcpu:16, dom:16;
> +            } d;
> +            d.dom = svc->vcpu->domain->domain_id;
> +            d.vcpu = svc->vcpu->vcpu_id;
> +            __trace_var(TRC_CSCHED2_RUNQ_CAND_CHECK, 1,
> +                        sizeof(d),
> +                        (unsigned char *)&d);
> +        }
> +
>          /* Only consider vcpus that are allowed to run on this processor. */
>          if ( !cpumask_test_cpu(cpu, svc->vcpu->cpu_hard_affinity) )
>          {
> @@ -2546,9 +2559,11 @@ runq_candidate(struct csched2_runqueue_data *rqd,
>          struct {
>              unsigned vcpu:16, dom:16;
>              unsigned tickled_cpu, skipped;
> +            int credit;
>          } d;
>          d.dom = snext->vcpu->domain->domain_id;
>          d.vcpu = snext->vcpu->vcpu_id;
> +        d.credit = snext->credit;
>          d.tickled_cpu = snext->tickled_cpu;
>          d.skipped = *skipped;
>          __trace_var(TRC_CSCHED2_RUNQ_CANDIDATE, 1,
>
>
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> Xen-devel@xxxxxxxxxxxxx
> https://lists.xen.org/xen-devel

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