Re: [dpdk-dev] [PATCH v2 2/3] examples/vm_power_manager: Allowing power managing of idle cores

["Hunt, David" <david.hunt@intel.com>]

Hi Rory,

On 18/5/2020 11:39 AM, Sexton, Rory wrote:
> This change is required to allow the branch ratio algorithm to
> power manage cores with no workload running on them. This is
> useful both when idle cores don't use C-states and for a number of
> hyperthreading scenarios.
>
> Signed-off-by: Rory Sexton <rory.sexton@intel.com>
> ---
>   examples/vm_power_manager/oob_monitor_x86.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/examples/vm_power_manager/oob_monitor_x86.c b/examples/vm_power_manager/oob_monitor_x86.c
> index 3c514475f..a5b1c168c 100644
> --- a/examples/vm_power_manager/oob_monitor_x86.c
> +++ b/examples/vm_power_manager/oob_monitor_x86.c
> @@ -96,12 +96,12 @@ apply_policy(int core)
>   	g_branch_misses = miss_diff;
>   
>   	if (hits_diff < (INTERVAL*100)) {
> -		/* Likely no workload running on this core. Skip. */
> -		return -1.0;
> +		/* Likely no workload running on this core. */
> +		ratio = 0.0;
> +	} else {
> +		ratio = (float)miss_diff * (float)100 / (float)hits_diff;
>   	}
>   
> -	ratio = (float)miss_diff * (float)100 / (float)hits_diff;
> -
>   	/*
>   	 * Store the last few directions that the ratio indicates
>   	 * we should take. If there's on 'up', then we scale up


Good enhancement. It hadn't occurred to me to manage non-PMD workloads, 
but I agree that when
C-States are disabled on a system, there may be cases where this 
algorithm is useful to save power.

Reviewed-by: David Hunt <david.hunt@intel.com>