[PATCH v2] storvsc: Set up correct queue depth values for IDE devices

[PATCH v2] storvsc: Set up correct queue depth values for IDE devices

[Long Li]

From: Long Li <longli@microsoft.com>

Unlike SCSI and FC, we don't use multiple channels for IDE.
Also fix the calculation for sub-channels.

Change log:
v2: Addressed comment on incorrect number of sub-channels.
(Michael Kelley <Michael.H.Kelley@microsoft.com>)

Signed-off-by: Long Li <longli@microsoft.com>
---
 drivers/scsi/storvsc_drv.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 8c51d628b52e..a2ec0bc9e9fa 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1722,11 +1722,14 @@ static int storvsc_probe(struct hv_device *device,
 		max_targets = STORVSC_MAX_TARGETS;
 		max_channels = STORVSC_MAX_CHANNELS;
 		/*
-		 * On Windows8 and above, we support sub-channels for storage.
+		 * On Windows8 and above, we support sub-channels for storage
+		 * on SCSI and FC controllers.
 		 * The number of sub-channels offerred is based on the number of
 		 * VCPUs in the guest.
 		 */
-		max_sub_channels = (num_cpus / storvsc_vcpus_per_sub_channel);
+		if (!dev_is_ide)
+			max_sub_channels =
+				(num_cpus - 1) / storvsc_vcpus_per_sub_channel;
 	}
 
 	scsi_driver.can_queue = (max_outstanding_req_per_channel *
-- 
2.14.1

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RE: [PATCH v2] storvsc: Set up correct queue depth values for IDE devices

[Michael Kelley (EOSG)]

> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org <linux-kernel-owner@vger.kernel.org> On Behalf
> Of Long Li
> Sent: Thursday, March 22, 2018 2:47 PM
> To: KY Srinivasan <kys@microsoft.com>; Haiyang Zhang <haiyangz@microsoft.com>; Stephen
> Hemminger <sthemmin@microsoft.com>; James E . J . Bottomley <JBottomley@odin.com>;
> Martin K . Petersen <martin.petersen@oracle.com>; devel@linuxdriverproject.org; linux-
> scsi@vger.kernel.org; linux-kernel@vger.kernel.org
> Cc: Long Li <longli@microsoft.com>
> Subject: [PATCH v2] storvsc: Set up correct queue depth values for IDE devices
> 
> From: Long Li <longli@microsoft.com>
> 
> Unlike SCSI and FC, we don't use multiple channels for IDE.
> Also fix the calculation for sub-channels.
> 
> Change log:
> v2: Addressed comment on incorrect number of sub-channels.
> (Michael Kelley <Michael.H.Kelley@microsoft.com>)
> 
> Signed-off-by: Long Li <longli@microsoft.com>

Reviewed-by: Michael Kelley <mikelley@microsoft.com>

> ---
>  drivers/scsi/storvsc_drv.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 8c51d628b52e..a2ec0bc9e9fa 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1722,11 +1722,14 @@ static int storvsc_probe(struct hv_device *device,
>  		max_targets = STORVSC_MAX_TARGETS;
>  		max_channels = STORVSC_MAX_CHANNELS;
>  		/*
> -		 * On Windows8 and above, we support sub-channels for storage.
> +		 * On Windows8 and above, we support sub-channels for storage
> +		 * on SCSI and FC controllers.
>  		 * The number of sub-channels offerred is based on the number of
>  		 * VCPUs in the guest.
>  		 */
> -		max_sub_channels = (num_cpus / storvsc_vcpus_per_sub_channel);
> +		if (!dev_is_ide)
> +			max_sub_channels =
> +				(num_cpus - 1) / storvsc_vcpus_per_sub_channel;
>  	}
> 
>  	scsi_driver.can_queue = (max_outstanding_req_per_channel *
> --
> 2.14.1

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RE: [PATCH v2] storvsc: Set up correct queue depth values for IDE devices

[Long Li]

Hi Martin

Can you take a look at the following patch?

Long

 
> > -----Original Message-----
> > From: linux-kernel-owner@vger.kernel.org
> > <linux-kernel-owner@vger.kernel.org> On Behalf Of Long Li
> > Sent: Thursday, March 22, 2018 2:47 PM
> > To: KY Srinivasan <kys@microsoft.com>; Haiyang Zhang
> > <haiyangz@microsoft.com>; Stephen Hemminger
> <sthemmin@microsoft.com>;
> > James E . J . Bottomley <JBottomley@odin.com>; Martin K . Petersen
> > <martin.petersen@oracle.com>; devel@linuxdriverproject.org; linux-
> > scsi@vger.kernel.org; linux-kernel@vger.kernel.org
> > Cc: Long Li <longli@microsoft.com>
> > Subject: [PATCH v2] storvsc: Set up correct queue depth values for IDE
> > devices
> >
> > From: Long Li <longli@microsoft.com>
> >
> > Unlike SCSI and FC, we don't use multiple channels for IDE.
> > Also fix the calculation for sub-channels.
> >
> > Change log:
> > v2: Addressed comment on incorrect number of sub-channels.
> > (Michael Kelley <Michael.H.Kelley@microsoft.com>)
> >
> > Signed-off-by: Long Li <longli@microsoft.com>
> 
> Reviewed-by: Michael Kelley <mikelley@microsoft.com>
> 
> > ---
> >  drivers/scsi/storvsc_drv.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> > index 8c51d628b52e..a2ec0bc9e9fa 100644
> > --- a/drivers/scsi/storvsc_drv.c
> > +++ b/drivers/scsi/storvsc_drv.c
> > @@ -1722,11 +1722,14 @@ static int storvsc_probe(struct hv_device
> *device,
> >  		max_targets = STORVSC_MAX_TARGETS;
> >  		max_channels = STORVSC_MAX_CHANNELS;
> >  		/*
> > -		 * On Windows8 and above, we support sub-channels for
> storage.
> > +		 * On Windows8 and above, we support sub-channels for
> storage
> > +		 * on SCSI and FC controllers.
> >  		 * The number of sub-channels offerred is based on the
> number of
> >  		 * VCPUs in the guest.
> >  		 */
> > -		max_sub_channels = (num_cpus /
> storvsc_vcpus_per_sub_channel);
> > +		if (!dev_is_ide)
> > +			max_sub_channels =
> > +				(num_cpus - 1) /
> storvsc_vcpus_per_sub_channel;
> >  	}
> >
> >  	scsi_driver.can_queue = (max_outstanding_req_per_channel *
> > --
> > 2.14.1

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Re: [PATCH v2] storvsc: Set up correct queue depth values for IDE devices

[Martin K. Petersen]

Long,

> Can you take a look at the following patch?

>> > + max_sub_channels =
>> > + 		(num_cpus - 1) / storvsc_vcpus_per_sub_channel;

What happens if num_cpus = 1?

-- 
Martin K. Petersen	Oracle Linux Engineering
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RE: [PATCH v2] storvsc: Set up correct queue depth values for IDE devices

[Long Li]

> Subject: Re: [PATCH v2] storvsc: Set up correct queue depth values for IDE
> devices
> 
> 
> Long,
> 
> > Can you take a look at the following patch?
> 
> >> > + max_sub_channels =
> >> > + 		(num_cpus - 1) / storvsc_vcpus_per_sub_channel;
> 
> What happens if num_cpus = 1?

If num_cpus=1, we don't have any sub channels.

The host offers one sub channel for VM with 5 CPUs, after that it offers an additional sub channel every 4 CPUs.

The primary channel is always offered.

> 
> --
> Martin K. Petersen	Oracle Linux Engineering
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Re: [PATCH v2] storvsc: Set up correct queue depth values for IDE devices

[Martin K. Petersen]

Long,

> If num_cpus=1, we don't have any sub channels.
>
> The host offers one sub channel for VM with 5 CPUs, after that it offers
> an additional sub channel every 4 CPUs.
>
> The primary channel is always offered.

Applied to 4.17/scsi-fixes. Thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering
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