Re: [Xen-devel] [PATCH 1/2] credit2: Fix erronous ASSERT

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.03.13 at 15:14, George Dunlap <george.dunlap@xxxxxxxxxxxxx> wrote:
> In order to avoid high-frequency cpu migration, vcpus may in fact be
> scheduled slightly out-of-order.  Account for this situation properly.
> 
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> ---
>  xen/common/sched_credit2.c |   40 ++++++++++++++++------------------------
>  1 file changed, 16 insertions(+), 24 deletions(-)
> 
> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
> index a7bd2ee..5bf5ebc 100644
> --- a/xen/common/sched_credit2.c
> +++ b/xen/common/sched_credit2.c
> @@ -1544,31 +1544,23 @@ csched_runtime(const struct scheduler *ops, int cpu, 
> struct csched_vcpu *snext)
>          }
>      }
>  
> -    /*
> -     * snext is about to be scheduled; so:
> -     *
> -     * 1. if snext->credit were less than 0 when it was taken off the
> -     * runqueue, then csched_schedule() should have called
> -     * reset_credit().  So at this point snext->credit must be greater
> -     * than 0.
> -     *
> -     * 2. snext's credit must be greater than or equal to anyone else
> -     * in the queue, so snext->credit - swait->credit must be greater
> -     * than or equal to 0.
> -     */
> -    ASSERT(rt_credit >= 0);
> -
> -    /* FIXME: See if we can eliminate this conversion if we know time
> -     * will be outside (MIN,MAX).  Probably requires pre-calculating
> -     * credit values of MIN,MAX per vcpu, since each vcpu burns credit
> -     * at a different rate. */
> -    time = c2t(rqd, rt_credit, snext);
> -
> -    /* Check limits */
> -    if ( time < CSCHED_MIN_TIMER )
> +    /* The next guy may actually have a higher credit, if we've */

This comment appears to end prematurely.

> +    if ( rt_credit < 0 )

Perhaps <= ?

Jan

>          time = CSCHED_MIN_TIMER;
> -    else if ( time > CSCHED_MAX_TIMER )
> -        time = CSCHED_MAX_TIMER;
> +    else
> +    {
> +        /* FIXME: See if we can eliminate this conversion if we know time
> +         * will be outside (MIN,MAX).  Probably requires pre-calculating
> +         * credit values of MIN,MAX per vcpu, since each vcpu burns credit
> +         * at a different rate. */
> +        time = c2t(rqd, rt_credit, snext);
> +
> +        /* Check limits */
> +        if ( time < CSCHED_MIN_TIMER )
> +            time = CSCHED_MIN_TIMER;
> +        else if ( time > CSCHED_MAX_TIMER )
> +            time = CSCHED_MAX_TIMER;
> +    }
>  
>      return time;
>  }
> -- 
> 1.7.9.5




_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel