Re: [Xen-devel] [PATCH for 4.7 3/4] xen: credit2: fix 2 (minor) issues in load tracking logic

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 03/05/16 22:46, Dario Faggioli wrote:
> All calculations that involve load_last_update uses quantities
> shifted by LOADAVG_GRANULARITY_SHIFT, so make sure that this
> is true even when the field is assigned a value for the first
> time, during vcpu allocation.
> 
> Also, during migration, while the loads of both the source and
> destination runqueues certainly need changing, the vcpu being
> moved does not change its running/non-running status, and its
> calculated load should hence not be affected.
> 
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

Looks good, thanks.

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

I suppose the code that sets 'svc->load_last_update = now' should
probably have changed the variable name to make it clear that now !=
NOW().  Maybe next time I'm looking through that code I'll do a bit of
renaming.

> ---
> Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  xen/common/sched_credit2.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
> index 803cc44..393364a 100644
> --- a/xen/common/sched_credit2.c
> +++ b/xen/common/sched_credit2.c
> @@ -867,7 +867,7 @@ csched2_alloc_vdata(const struct scheduler *ops, struct 
> vcpu *vc, void *dd)
>          svc->weight = svc->sdom->weight;
>          /* Starting load of 50% */
>          svc->avgload = 1ULL << (CSCHED2_PRIV(ops)->load_window_shift - 1);
> -        svc->load_last_update = NOW();
> +        svc->load_last_update = NOW() >> LOADAVG_GRANULARITY_SHIFT;
>      }
>      else
>      {
> @@ -1301,7 +1301,7 @@ static void migrate(const struct scheduler *ops,
>          if ( __vcpu_on_runq(svc) )
>          {
>              __runq_remove(svc);
> -            update_load(ops, svc->rqd, svc, -1, now);
> +            update_load(ops, svc->rqd, NULL, -1, now);
>              on_runq=1;
>          }
>          __runq_deassign(svc);
> @@ -1314,7 +1314,7 @@ static void migrate(const struct scheduler *ops,
>          __runq_assign(svc, trqd);
>          if ( on_runq )
>          {
> -            update_load(ops, svc->rqd, svc, 1, now);
> +            update_load(ops, svc->rqd, NULL, 1, now);
>              runq_insert(ops, svc->vcpu->processor, svc);
>              runq_tickle(ops, svc->vcpu->processor, svc, now);
>              SCHED_STAT_CRANK(migrate_on_runq);
> 


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