scsi: storvsc: Correctly set number of hardware queues for IDE disk
authorLong Li <longli@microsoft.com>
Tue, 14 Jan 2020 00:08:36 +0000 (16:08 -0800)
committerMartin K. Petersen <martin.petersen@oracle.com>
Thu, 16 Jan 2020 04:02:24 +0000 (23:02 -0500)
commit7b571c19d4c0b78d27dd3bf1f3c42e4032390af6
treefb61a98dda7889e07c6641f02792019275f9b04a
parent42ec15ceaea74b5f7a621fc6686cbf69ca66c4cf
scsi: storvsc: Correctly set number of hardware queues for IDE disk

Commit 0ed881027690 ("scsi: storvsc: setup 1:1 mapping between hardware
queue and CPU queue") introduced a regression for disks attached to
IDE. For these disks the host VSP only offers one VMBUS channel. Setting
multiple queues can overload the VMBUS channel and result in performance
drop for high queue depth workload on system with large number of CPUs.

Fix it by leaving the number of hardware queues to 1 (default value) for
IDE disks.

Fixes: 0ed881027690 ("scsi: storvsc: setup 1:1 mapping between hardware queue and CPU queue")
Link: https://lore.kernel.org/r/1578960516-108228-1-git-send-email-longli@linuxonhyperv.com
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
drivers/scsi/storvsc_drv.c