netdev - Re: [PATCH net] bnxt_en: use irq_update_affinity

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Message-ID: <Zyv6ncZSVR5mohsF@JRM7P7Q02P>
Date: Wed, 6 Nov 2024 18:24:13 -0500
From: Andy Gospodarek <andrew.gospodarek@...adcom.com>
To: Mohammad Heib <mheib@...hat.com>
Cc: netdev@...r.kernel.org, michael.chan@...adcom.com, skotur@...adcom.com
Subject: Re: [PATCH net] bnxt_en: use irq_update_affinity_hint()

On Wed, Nov 06, 2024 at 08:08:11PM +0200, Mohammad Heib wrote:
> irq_set_affinity_hint() is deprecated, Use irq_update_affinity_hint()
> instead. This removes the side-effect of actually applying the affinity.
> 
> The driver does not really need to worry about spreading its IRQs across
> CPUs. The core code already takes care of that. when the driver applies the
> affinities by itself, it breaks the users' expectations:
> 
>  1. The user configures irqbalance with IRQBALANCE_BANNED_CPULIST in
>     order to prevent IRQs from being moved to certain CPUs that run a
>     real-time workload.
> 
>  2. bnxt_en device reopening will resets the affinity
>     in bnxt_open().
> 
>  3. bnxt_en has no idea about irqbalance's config, so it may move an IRQ to
>     a banned CPU. The real-time workload suffers unacceptable latency.
> 

Thanks for the patch.  This seems inline with what have been done in other
drivers.

> Signed-off-by: Mohammad Heib <mheib@...hat.com>
Reviewed-by: Andy Gospodarek <gospo@...adcom.com>

> ---
>  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index 99d025b69079..cd82f93b20a1 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -10885,7 +10885,7 @@ static void bnxt_free_irq(struct bnxt *bp)
>  		irq = &bp->irq_tbl[map_idx];
>  		if (irq->requested) {
>  			if (irq->have_cpumask) {
> -				irq_set_affinity_hint(irq->vector, NULL);
> +				irq_update_affinity_hint(irq->vector, NULL);
>  				free_cpumask_var(irq->cpu_mask);
>  				irq->have_cpumask = 0;
>  			}
> @@ -10940,10 +10940,10 @@ static int bnxt_request_irq(struct bnxt *bp)
>  			irq->have_cpumask = 1;
>  			cpumask_set_cpu(cpumask_local_spread(i, numa_node),
>  					irq->cpu_mask);
> -			rc = irq_set_affinity_hint(irq->vector, irq->cpu_mask);
> +			rc = irq_update_affinity_hint(irq->vector, irq->cpu_mask);
>  			if (rc) {
>  				netdev_warn(bp->dev,
> -					    "Set affinity failed, IRQ = %d\n",
> +					    "Update affinity hint failed, IRQ = %d\n",
>  					    irq->vector);
>  				break;
>  			}
> -- 
> 2.34.3
>