From: Long Li longli@microsoft.com
[ Upstream commit 7b571c19d4c0b78d27dd3bf1f3c42e4032390af6 ]
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@linuxonh... 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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/scsi/storvsc_drv.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index 542d2bac2922c..5087ed6afbdc3 100644 --- a/drivers/scsi/storvsc_drv.c +++ b/drivers/scsi/storvsc_drv.c @@ -1835,9 +1835,11 @@ static int storvsc_probe(struct hv_device *device, */ host->sg_tablesize = (stor_device->max_transfer_bytes >> PAGE_SHIFT); /* + * For non-IDE disks, the host supports multiple channels. * Set the number of HW queues we are supporting. */ - host->nr_hw_queues = num_present_cpus(); + if (!dev_is_ide) + host->nr_hw_queues = num_present_cpus();
/* * Set the error handler work queue.