Re: [PATCH v3 3/3] examples/l3fwd-power: enable PMD power monitor on Arm

[Thomas Monjalon <thomas@monjalon.net>]

11/11/2022 08:26, Feifei Wang:
> For Arm aarch, power monitor uses WFE instruction to enable, which can
> not exit automatically within the time limit. This means
> 'rte_power_monitor_wakeup' API needs to be called to wake up sleep cores
> if there is no store operation to monitored address.
> 
> Furthermore, we disable power monitor feature on the main core so that
> it can be used to wake up other sleeping cores after it exit from loop.
> 
> Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> Acked-by: David Hunt <david.hunt@intel.com>
> ---
> +#if defined(RTE_ARCH_ARM64)
> +				/* Ensure the main lcore does not enter the power-monitor state,
> +				 * so that it can be used to wake up other lcores on ARM.
> +				 * This is due to WFE instruction has no timeout wake-up mechanism,
> +				 * and if users want to exit actively, the main lcore is needed
> +				 * to send SEV instruction to wake up other lcores.
> +				 */
> +				unsigned int main_lcore = rte_get_main_lcore();
> +				if (lcore_id == main_lcore &&
> +						pmgmt_type == RTE_POWER_MGMT_TYPE_MONITOR)
> +					continue;
> +#endif

We need to have this logic abstracted in the API for all architectures.
We cannot afford having such #ifdef per CPU in the application.