Re: [PATCH v1 1/7] mpi3mr: Add module parameter to control threaded IRQ polling

[Damien Le Moal <dlemoal@kernel.org>]

On 1/12/26 09:10, Ranjan Kumar wrote:
> Add a module parameter to enable or disable threaded IRQ polling
> in the driver. The default behavior remains unchanged
> with polling enabled.
> 
> When disabled, completion processing is kept entirely in the
> hard IRQ context, avoiding the threaded polling path.

What does that bring ? Better throughput ? Lower latency ? please tell us more
about the benefits of this change.

> 
> Signed-off-by: Ranjan Kumar <ranjan.kumar@broadcom.com>
> ---
>  drivers/scsi/mpi3mr/mpi3mr_fw.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/mpi3mr/mpi3mr_fw.c b/drivers/scsi/mpi3mr/mpi3mr_fw.c
> index 8fe6e0bf342e..869e525f3e73 100644
> --- a/drivers/scsi/mpi3mr/mpi3mr_fw.c
> +++ b/drivers/scsi/mpi3mr/mpi3mr_fw.c
> @@ -21,6 +21,10 @@ static int mpi3mr_check_op_admin_proc(struct mpi3mr_ioc *mrioc);
>  static int poll_queues;
>  module_param(poll_queues, int, 0444);
>  MODULE_PARM_DESC(poll_queues, "Number of queues for io_uring poll mode. (Range 1 - 126)");
> +static bool threaded_isr_poll = true;
> +module_param(threaded_isr_poll, bool, 0444);
> +MODULE_PARM_DESC(threaded_isr_poll,
> +			"Enablement of IRQ polling thread (default=true)");
>  
>  #if defined(writeq) && defined(CONFIG_64BIT)
>  static inline void mpi3mr_writeq(__u64 b, void __iomem *addr,
> @@ -595,7 +599,8 @@ int mpi3mr_process_op_reply_q(struct mpi3mr_ioc *mrioc,
>  		 * Exit completion loop to avoid CPU lockup
>  		 * Ensure remaining completion happens from threaded ISR.
>  		 */
> -		if (num_op_reply > mrioc->max_host_ios) {
> +		if ((num_op_reply > mrioc->max_host_ios) &&
> +			(threaded_isr_poll == true)) {
>  			op_reply_q->enable_irq_poll = true;
>  			break;
>  		}
> @@ -692,7 +697,7 @@ static irqreturn_t mpi3mr_isr(int irq, void *privdata)
>  	 * If more IOs are expected, schedule IRQ polling thread.
>  	 * Otherwise exit from ISR.
>  	 */
> -	if (!intr_info->op_reply_q)
> +	if ((threaded_isr_poll == false) || !intr_info->op_reply_q)
>  		return ret;
>  
>  	if (!intr_info->op_reply_q->enable_irq_poll ||


-- 
Damien Le Moal
Western Digital Research