From: "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
Date: Wed, 24 Jan 2018 22:14:08 +0000
Patch-mainline: v4.16-rc5
Subject: scsi: storvsc: Spread interrupts when picking a channel for I/O requests
Git-commit: 9cfad4a5f4f795715c8657fb7dc22574a6046327
References: fate#323887
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@microsoft.com>
Reviewed-by: Long Li <longli@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Olaf Hering <ohering@suse.de>
---
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
--- 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];