From: Long Li <[email protected]>
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")
Signed-off-by: Long Li <[email protected]>
---
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 f8faf8b3d965..992b28e40374 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1842,9 +1842,11 @@ 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_id->driver_data != IDE_GUID)
+ host->nr_hw_queues = num_present_cpus();
/*
* Set the error handler work queue.
--
2.20.1
On Sat, Jan 11, 2020 at 4:17 PM <[email protected]> wrote:
>
> From: Long Li <[email protected]>
>
> 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")
> Signed-off-by: Long Li <[email protected]>
> ---
> 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 f8faf8b3d965..992b28e40374 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1842,9 +1842,11 @@ 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_id->driver_data != IDE_GUID)
> + host->nr_hw_queues = num_present_cpus();
>
> /*
> * Set the error handler work queue.
> --
> 2.20.1
>
Reviewed-by: Ming Lei <[email protected]>
--
Ming Lei
From: Long Li <[email protected]> Sent: Saturday, January 11, 2020 12:17 AM
>
> 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")
> Signed-off-by: Long Li <[email protected]>
> ---
> 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 f8faf8b3d965..992b28e40374 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1842,9 +1842,11 @@ 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_id->driver_data != IDE_GUID)
This function already has a pre-computed value of this test in
the local variable "dev_is_ide". It would be more consistent
to just use it.
Michael
> + host->nr_hw_queues = num_present_cpus();
>
> /*
> * Set the error handler work queue.
> --
> 2.20.1
>Subject: RE: [PATCH] scsi: storvsc: Correctly set number of hardware queues for
>IDE disk
>
>From: Long Li <[email protected]> Sent: Saturday, January 11, 2020 12:17
>AM
>>
>> 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")
>> Signed-off-by: Long Li <[email protected]>
>> ---
>> 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 f8faf8b3d965..992b28e40374 100644
>> --- a/drivers/scsi/storvsc_drv.c
>> +++ b/drivers/scsi/storvsc_drv.c
>> @@ -1842,9 +1842,11 @@ 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_id->driver_data != IDE_GUID)
>
>This function already has a pre-computed value of this test in
>the local variable "dev_is_ide". It would be more consistent
>to just use it.
>
>Michael
I will send v2 to address this.
Long
>
>> + host->nr_hw_queues = num_present_cpus();
>>
>> /*
>> * Set the error handler work queue.
>> --
>> 2.20.1