[PATCH 1/1] scsi: storvsc: Spread interrupts when picking a channel for I/O requests

[Michael Kelley (EOSG)]

Updated/corrected two email addresses ...

> -----Original Message-----
> From: Michael Kelley (EOSG)
> Sent: Wednesday, January 24, 2018 2:14 PM
> To: KY Srinivasan <kys at microsoft.com>; Stephen Hemminger <sthemmin at microsoft.com>;
> martin.petersen at oracle.com; longi at microsoft.com; JBottomley at odin.com;
> devel at linuxdriverproject.org; linux-kernel at vger.kernel.org; linux-scsi at vger.kernel.org
> Cc: Michael Kelley (EOSG) <Michael.H.Kelley at microsoft.com>
> Subject: [PATCH 1/1] scsi: storvsc: Spread interrupts when picking a channel for I/O requests
> 
> Update the algorithm in storvsc_do_io to look for a channel
> starting with the current CPU + 1 and wrap around (within the
> current NUMA node). This spreads VMbus interrupts more evenly
> across CPUs. Previous code always started with first CPU in
> the current NUMA node, skewing the interrupt load to that CPU.
> 
> Signed-off-by: Michael Kelley <mikelley at microsoft.com>
> ---
>  drivers/scsi/storvsc_drv.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index e07907d..f3264c4 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1310,7 +1310,8 @@ static int storvsc_do_io(struct hv_device *device,
>  			 */
>  			cpumask_and(&alloced_mask, &stor_device->alloced_cpus,
>  				    cpumask_of_node(cpu_to_node(q_num)));
> -			for_each_cpu(tgt_cpu, &alloced_mask) {
> +			for_each_cpu_wrap(tgt_cpu, &alloced_mask,
> +					outgoing_channel->target_cpu + 1) {
>  				if (tgt_cpu != outgoing_channel->target_cpu) {
>  					outgoing_channel =
>  					stor_device->stor_chns[tgt_cpu];
> --
> 1.8.3.1