Re: [dpdk-stable] [dpdk-dev] [PATCH 2/2] l3fwd-power: fix interrupt disable

[Harman Kalra <hkalra@marvell.com>]

On Mon, Jan 20, 2020 at 10:06:57PM -0500, Xiao Wang wrote:
> Since all related queues' interrupts are turned on before epoll, we need
> to turn off all the interrupts after wakeup. This patch fixes the issue
> of only turning off the interrupted queues.
> 
> Fixes: b736d64787fc ("examples/l3fwd-power: disable Rx interrupt when waking up")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
> ---
>  examples/l3fwd-power/main.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/examples/l3fwd-power/main.c b/examples/l3fwd-power/main.c
> index ffcc7ecf4..e9b2cb5b3 100644
> --- a/examples/l3fwd-power/main.c
> +++ b/examples/l3fwd-power/main.c
> @@ -880,9 +880,6 @@ sleep_until_rx_interrupt(int num)
>  		port_id = ((uintptr_t)data) >> CHAR_BIT;
>  		queue_id = ((uintptr_t)data) &
>  			RTE_LEN2MASK(CHAR_BIT, uint8_t);
> -		rte_spinlock_lock(&(locks[port_id]));
> -		rte_eth_dev_rx_intr_disable(port_id, queue_id);
> -		rte_spinlock_unlock(&(locks[port_id]));
>  		RTE_LOG(INFO, L3FWD_POWER,
>  			"lcore %u is waked up from rx interrupt on"
>  			" port %d queue %d\n",
> @@ -892,7 +889,7 @@ sleep_until_rx_interrupt(int num)
>  	return 0;
>  }
>  
> -static void turn_on_intr(struct lcore_conf *qconf)
> +static void turn_on_off_intr(struct lcore_conf *qconf, bool on)
>  {
>  	int i;
>  	struct lcore_rx_queue *rx_queue;
> @@ -905,7 +902,10 @@ static void turn_on_intr(struct lcore_conf *qconf)
>  		queue_id = rx_queue->queue_id;
>  
>  		rte_spinlock_lock(&(locks[port_id]));
> -		rte_eth_dev_rx_intr_enable(port_id, queue_id);
> +		if (on)
> +			rte_eth_dev_rx_intr_enable(port_id, queue_id);
> +		else
> +			rte_eth_dev_rx_intr_disable(port_id, queue_id);

Hi Wang

I tested this patch on octeontx2 platform and have some queries
regarding the same:
Difference what I observed with this patch is, you are disabling
interrupts for all the queues handled by the core which woke up but
what is the advantage of doing so? 
I dont see any difference wrt octeontx2, with and without this patch in
term of power saving. Can you please explain what I am missing.

Thanks
Harman

>  		rte_spinlock_unlock(&(locks[port_id]));
>  	}
>  }
> @@ -1340,9 +1340,10 @@ main_loop(__attribute__((unused)) void *dummy)
>  			else {
>  				/* suspend until rx interrupt triggers */
>  				if (intr_en) {
> -					turn_on_intr(qconf);
> +					turn_on_off_intr(qconf, 1);
>  					sleep_until_rx_interrupt(
>  						qconf->n_rx_queue);
> +					turn_on_off_intr(qconf, 0);
>  					/**
>  					 * start receiving packets immediately
>  					 */
> -- 
> 2.15.1
>