Re: [PATCH v2] sched: print information about scheduling granularity

[Jürgen Groß <jgross@xxxxxxxx>]

On 20.04.20 15:06, Sergey Dyasli wrote:
> Currently it might be not obvious which scheduling mode (e.g. core-
> scheduling) is being used by the scheduler. Alleviate this by printing
> additional information about the selected granularity per-cpupool.
>
> Note: per-cpupool granularity selection is not implemented yet.
>        The single global value is being used for each cpupool.
This is misleading. You are using the per-cpupool values, but they
are all the same right now.

> Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
> ---
> v2:
> - print information on a separate line
> - use per-cpupool granularity
> - updated commit message
>
> CC: Juergen Gross <jgross@xxxxxxxx>
> CC: Dario Faggioli <dfaggioli@xxxxxxxx>
> CC: George Dunlap <george.dunlap@xxxxxxxxxx>
> CC: Jan Beulich <jbeulich@xxxxxxxx>
> ---
>   xen/common/sched/cpupool.c | 26 ++++++++++++++++++++++++++
>   1 file changed, 26 insertions(+)
>
> diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
> index d40345b585..68106f6c15 100644
> --- a/xen/common/sched/cpupool.c
> +++ b/xen/common/sched/cpupool.c
> @@ -40,6 +40,30 @@ static DEFINE_SPINLOCK(cpupool_lock);
>   static enum sched_gran __read_mostly opt_sched_granularity = SCHED_GRAN_cpu;
>   static unsigned int __read_mostly sched_granularity = 1;
>   
> +static void sched_gran_print(enum sched_gran mode, unsigned int gran)
> +{
> +    char *str = "";
> +
> +    switch ( mode )
> +    {
> +    case SCHED_GRAN_cpu:
> +        str = "cpu";
> +        break;
> +    case SCHED_GRAN_core:
> +        str = "core";
> +        break;
> +    case SCHED_GRAN_socket:
> +        str = "socket";
> +        break;
> +    default:
> +        ASSERT_UNREACHABLE();
> +        break;
> +    }
With this addition it might make sense to have an array indexed by
mode to get the string. This array could then be used in
sched_select_granularity(), too.

> +
> +    printk("Scheduling granularity: %s, %u CPU%s per sched-resource\n",
> +           str, gran, gran == 1 ? "" : "s");
> +}
> +
>   #ifdef CONFIG_HAS_SCHED_GRANULARITY
>   static int __init sched_select_granularity(const char *str)
>   {
> @@ -115,6 +139,7 @@ static void __init cpupool_gran_init(void)
>           warning_add(fallback);
>   
>       sched_granularity = gran;
> +    sched_gran_print(opt_sched_granularity, sched_granularity);
>   }
>   
>   unsigned int cpupool_get_granularity(const struct cpupool *c)
> @@ -911,6 +936,7 @@ void dump_runq(unsigned char key)
>       {
>           printk("Cpupool %d:\n", (*c)->cpupool_id);
>           printk("Cpus: %*pbl\n", CPUMASK_PR((*c)->cpu_valid));
> +        sched_gran_print((*c)->gran, cpupool_get_granularity(*c));
>           schedule_dump(*c);
>       }

Juergen