[PATCH 0/2] DisplayLink USB-ethernet improvements

[PATCH 0/2] DisplayLink USB-ethernet improvements

[Łukasz Spintzyk]

Hi all,

I am resending that two changes again.

This are two patches to cdc_ncm driver used in our DisplayLink USB docking stations.
They are independent, however both of them are improving performance and stability so it matches Windows experience.

It is improving the experience for users of millions of DisplayLink-based docking stations that are in the wild.
That tweaks of NTB TX/RX results in approximately 4-5x available bandwidth improvement in extreme cases.


Please take a look. 

Regards,
Łukasz Spintzyk 

Software Developer at Synaptics Inc.


Dominik Czerwik (1):
  net/cdc_ncm: Enable ZLP for DisplayLink ethernet devices

Łukasz Spintzyk (1):
  net/cdc_ncm: Increase NTB max RX/TX values to 64kb

 drivers/net/usb/cdc_ncm.c   | 24 ++++++++++++++++++++++++
 include/linux/usb/cdc_ncm.h |  4 ++--
 2 files changed, 26 insertions(+), 2 deletions(-)

-- 
2.36.1

[PATCH 1/2] net/cdc_ncm: Enable ZLP for DisplayLink ethernet devices

[Łukasz Spintzyk]

From: Dominik Czerwik <dominik.czerwik@synaptics.com>

This improves performance and stability of
DL-3xxx/DL-5xxx/DL-6xxx device series.

Signed-off-by: Dominik Czerwik <dominik.czerwik@synaptics.com>
Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
---
 drivers/net/usb/cdc_ncm.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index d55f59ce4a31..4594bf2982ee 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -2,6 +2,7 @@
  * cdc_ncm.c
  *
  * Copyright (C) ST-Ericsson 2010-2012
+ * Copyright (C) 2022 Synaptics Incorporated. All rights reserved.
  * Contact: Alexey Orishko <alexey.orishko@stericsson.com>
  * Original author: Hans Petter Selasky <hans.petter.selasky@stericsson.com>
  *
@@ -1904,6 +1905,19 @@ static const struct driver_info cdc_ncm_info = {
 	.set_rx_mode = usbnet_cdc_update_filter,
 };
 
+/* Same as cdc_ncm_info, but with FLAG_SEND_ZLP  */
+static const struct driver_info cdc_ncm_zlp_info = {
+	.description = "CDC NCM (SEND ZLP)",
+	.flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
+			| FLAG_LINK_INTR | FLAG_ETHER | FLAG_SEND_ZLP,
+	.bind = cdc_ncm_bind,
+	.unbind = cdc_ncm_unbind,
+	.manage_power = usbnet_manage_power,
+	.status = cdc_ncm_status,
+	.rx_fixup = cdc_ncm_rx_fixup,
+	.tx_fixup = cdc_ncm_tx_fixup,
+};
+
 /* Same as cdc_ncm_info, but with FLAG_WWAN */
 static const struct driver_info wwan_info = {
 	.description = "Mobile Broadband Network Device",
@@ -2010,6 +2024,16 @@ static const struct usb_device_id cdc_devs[] = {
 	  .driver_info = (unsigned long)&wwan_info,
 	},
 
+	/* DisplayLink docking stations */
+	{ .match_flags = USB_DEVICE_ID_MATCH_INT_INFO
+		| USB_DEVICE_ID_MATCH_VENDOR,
+	  .idVendor = 0x17e9,
+	  .bInterfaceClass = USB_CLASS_COMM,
+	  .bInterfaceSubClass = USB_CDC_SUBCLASS_NCM,
+	  .bInterfaceProtocol = USB_CDC_PROTO_NONE,
+	  .driver_info = (unsigned long)&cdc_ncm_zlp_info,
+	},
+
 	/* Generic CDC-NCM devices */
 	{ USB_INTERFACE_INFO(USB_CLASS_COMM,
 		USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
-- 
2.36.1

[PATCH 2/2] net/cdc_ncm: Increase NTB max RX/TX values to 64kb

[Łukasz Spintzyk]

DisplayLink ethernet devices require NTB buffers larger then 32kb in order to run with highest performance.

Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
---
 include/linux/usb/cdc_ncm.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
index f7cb3ddce7fb..2d207cb4837d 100644
--- a/include/linux/usb/cdc_ncm.h
+++ b/include/linux/usb/cdc_ncm.h
@@ -53,8 +53,8 @@
 #define USB_CDC_NCM_NDP32_LENGTH_MIN		0x20
 
 /* Maximum NTB length */
-#define	CDC_NCM_NTB_MAX_SIZE_TX			32768	/* bytes */
-#define	CDC_NCM_NTB_MAX_SIZE_RX			32768	/* bytes */
+#define	CDC_NCM_NTB_MAX_SIZE_TX			65536	/* bytes */
+#define	CDC_NCM_NTB_MAX_SIZE_RX			65536	/* bytes */
 
 /* Initial NTB length */
 #define	CDC_NCM_NTB_DEF_SIZE_TX			16384	/* bytes */
-- 
2.36.1

Re: [PATCH 2/2] net/cdc_ncm: Increase NTB max RX/TX values to 64kb

[Greg KH]

On Mon, Jul 04, 2022 at 09:04:07AM +0200, Łukasz Spintzyk wrote:
> DisplayLink ethernet devices require NTB buffers larger then 32kb in order to run with highest performance.
> 
> Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
> ---
>  include/linux/usb/cdc_ncm.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
> index f7cb3ddce7fb..2d207cb4837d 100644
> --- a/include/linux/usb/cdc_ncm.h
> +++ b/include/linux/usb/cdc_ncm.h
> @@ -53,8 +53,8 @@
>  #define USB_CDC_NCM_NDP32_LENGTH_MIN		0x20
>  
>  /* Maximum NTB length */
> -#define	CDC_NCM_NTB_MAX_SIZE_TX			32768	/* bytes */
> -#define	CDC_NCM_NTB_MAX_SIZE_RX			32768	/* bytes */
> +#define	CDC_NCM_NTB_MAX_SIZE_TX			65536	/* bytes */
> +#define	CDC_NCM_NTB_MAX_SIZE_RX			65536	/* bytes */

Does this mess with the throughput of older devices that are not on
displaylink connections?

What devices did you test this on, and what is the actual performance
changes?  You offer no real information here at all, and large buffer
sizes does have other downsides, so determining how you tested this is
key.

Also, please wrap your changelogs at 72 columns like git asks you to do.

thanks,

greg k-h

Re: [PATCH 1/2] net/cdc_ncm: Enable ZLP for DisplayLink ethernet devices

[Greg KH]

On Mon, Jul 04, 2022 at 09:04:06AM +0200, Łukasz Spintzyk wrote:
> From: Dominik Czerwik <dominik.czerwik@synaptics.com>
> 
> This improves performance and stability of
> DL-3xxx/DL-5xxx/DL-6xxx device series.
> 
> Signed-off-by: Dominik Czerwik <dominik.czerwik@synaptics.com>
> Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
> ---
>  drivers/net/usb/cdc_ncm.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
> index d55f59ce4a31..4594bf2982ee 100644
> --- a/drivers/net/usb/cdc_ncm.c
> +++ b/drivers/net/usb/cdc_ncm.c
> @@ -2,6 +2,7 @@
>   * cdc_ncm.c
>   *
>   * Copyright (C) ST-Ericsson 2010-2012
> + * Copyright (C) 2022 Synaptics Incorporated. All rights reserved.

As I ask many times for other copyright additions, when making a change
like this, for such a tiny patch, I want to see a lawyer from your
company also sign off on the patch proving that they agree that this
line should be added.

thanks,

greg k-h

Re: [PATCH 2/2] net/cdc_ncm: Increase NTB max RX/TX values to 64kb

[Lukasz Spintzyk]

On 04/07/2022 09:24, Greg KH wrote:
> CAUTION: Email originated externally, do not click links or open attachments unless you recognize the sender and know the content is safe.
> 
> 
> On Mon, Jul 04, 2022 at 09:04:07AM +0200, Łukasz Spintzyk wrote:
>> DisplayLink ethernet devices require NTB buffers larger then 32kb in order to run with highest performance.
>>
>> Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
>> ---
>>   include/linux/usb/cdc_ncm.h | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
>> index f7cb3ddce7fb..2d207cb4837d 100644
>> --- a/include/linux/usb/cdc_ncm.h
>> +++ b/include/linux/usb/cdc_ncm.h
>> @@ -53,8 +53,8 @@
>>   #define USB_CDC_NCM_NDP32_LENGTH_MIN         0x20
>>
>>   /* Maximum NTB length */
>> -#define      CDC_NCM_NTB_MAX_SIZE_TX                 32768   /* bytes */
>> -#define      CDC_NCM_NTB_MAX_SIZE_RX                 32768   /* bytes */
>> +#define      CDC_NCM_NTB_MAX_SIZE_TX                 65536   /* bytes */
>> +#define      CDC_NCM_NTB_MAX_SIZE_RX                 65536   /* bytes */
> 
> Does this mess with the throughput of older devices that are not on
> displaylink connections?
> 
> What devices did you test this on, and what is the actual performance
> changes?  You offer no real information here at all, and large buffer
> sizes does have other downsides, so determining how you tested this is
> key.
> 
> Also, please wrap your changelogs at 72 columns like git asks you to do.
> 
> thanks,
> 
> greg k-h

Hi Greg,
To my best knowledge that patch should not affect other devices because:
  - tx,rx buffers size is initialized to 16kb with 
CDC_NCM_NTB_DEF_SIZE_RX, and CDC_NCM_NTB_DEF_SIZE_TX
    So all existing devices should not be affected by default.
  - In order to change tx and rx buffer max size you need to 
additionally modify cdc_ncm/tx_max and cdc_ncm/rx_max parameters. This 
can be done with udev rules and ethtool. So if you want to use higher 
buffer sizes you need to specially request that.
For DisplayLink devices this will be done with udev rule that will be 
installed with other DisplayLink drivers.
   - This tx,rx buffer sizes are always capped to dwNtbMaxInMaxSize and 
dwNtbMaxOutMaxSize that are advertised by the device itself. So in 
theory that values should be acceptable by the device.

Here is summary of my tests I have done on such devices:
  - DisplayLink DL-3xxx family device
  - DisplayLink DL-6xxx family device
  - ASUS USB-C2500 2.5G USB3 eth adapter
  - Plugable USB3 1G USB3 adapter
  - EDIMAX EU-4307 USB-C adapter
  - Dell DBQBCBC064 USB-C adapter

Unfortunately I was not able to find more or older than USB-3 device on 
company's shelf.

I was doing measurements with:
  - iperf3 between two linux boxes
  - http://openspeedtest.com/ instance running on local testing machine

I can provide you with detailed results, but I think they are quite 
verbose so I will stay with some high level results:

- All except one from third party usb adapters were not affected by 
increased buffer size. (I have forced them to use tx,rx size as big as 
their advertised dwNtbOutMaxSize and dwNtbInMaxSize).
   They were generally reaching 912 - 940Mbps (download/upload)
   Only Edimax adapter experienced decreased download size from 929Mbps 
to 827 with iper3. In openspeedtest this was decrease from 968Mbps to 
886Mbps

- DisplayLink DL-3xxx family devices experienced increase of performance
   Iperf3:
    Download from (300Mbps to 870Mbps), also from historical 
measurements      on other setup this was (90Mbps to 500Mbps)
    Upload from 782Mbps to 844Mbps
   Openspeedtest:
    Download from 556Mbps to 873Mbps
    Upload from 727Mbps to 973Mbps

- DiplayLink DL-6xxx family devices are not affected greatly by buffer 
size. It is more affected by patch enabling ZLP which prevents device 
from temporary network dropouts when playing video from web and network 
traffic going through it is high.

thanks
Łukasz Spintzyk

Re: [PATCH 1/2] net/cdc_ncm: Enable ZLP for DisplayLink ethernet devices

[Lukasz Spintzyk]

On 04/07/2022 09:25, Greg KH wrote:
> CAUTION: Email originated externally, do not click links or open attachments unless you recognize the sender and know the content is safe.
> 
> 
> On Mon, Jul 04, 2022 at 09:04:06AM +0200, Łukasz Spintzyk wrote:
>> From: Dominik Czerwik <dominik.czerwik@synaptics.com>
>>
>> This improves performance and stability of
>> DL-3xxx/DL-5xxx/DL-6xxx device series.
>>
>> Signed-off-by: Dominik Czerwik <dominik.czerwik@synaptics.com>
>> Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
>> ---
>>   drivers/net/usb/cdc_ncm.c | 24 ++++++++++++++++++++++++
>>   1 file changed, 24 insertions(+)
>>
>> diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
>> index d55f59ce4a31..4594bf2982ee 100644
>> --- a/drivers/net/usb/cdc_ncm.c
>> +++ b/drivers/net/usb/cdc_ncm.c
>> @@ -2,6 +2,7 @@
>>    * cdc_ncm.c
>>    *
>>    * Copyright (C) ST-Ericsson 2010-2012
>> + * Copyright (C) 2022 Synaptics Incorporated. All rights reserved.
> 
> As I ask many times for other copyright additions, when making a change
> like this, for such a tiny patch, I want to see a lawyer from your
> company also sign off on the patch proving that they agree that this
> line should be added.
> 
> thanks,
> 
> greg k-h

Ok, I will contact company's layer and will be back with updated patches 
if needed.
thanks
Łukasz Spintzyk

Re: [PATCH 2/2] net/cdc_ncm: Increase NTB max RX/TX values to 64kb

[Greg KH]

On Fri, Jul 08, 2022 at 09:40:49AM +0200, Lukasz Spintzyk wrote:
> On 04/07/2022 09:24, Greg KH wrote:
> > CAUTION: Email originated externally, do not click links or open attachments unless you recognize the sender and know the content is safe.
> > 
> > 
> > On Mon, Jul 04, 2022 at 09:04:07AM +0200, Łukasz Spintzyk wrote:
> > > DisplayLink ethernet devices require NTB buffers larger then 32kb in order to run with highest performance.
> > > 
> > > Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
> > > ---
> > >   include/linux/usb/cdc_ncm.h | 4 ++--
> > >   1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
> > > index f7cb3ddce7fb..2d207cb4837d 100644
> > > --- a/include/linux/usb/cdc_ncm.h
> > > +++ b/include/linux/usb/cdc_ncm.h
> > > @@ -53,8 +53,8 @@
> > >   #define USB_CDC_NCM_NDP32_LENGTH_MIN         0x20
> > > 
> > >   /* Maximum NTB length */
> > > -#define      CDC_NCM_NTB_MAX_SIZE_TX                 32768   /* bytes */
> > > -#define      CDC_NCM_NTB_MAX_SIZE_RX                 32768   /* bytes */
> > > +#define      CDC_NCM_NTB_MAX_SIZE_TX                 65536   /* bytes */
> > > +#define      CDC_NCM_NTB_MAX_SIZE_RX                 65536   /* bytes */
> > 
> > Does this mess with the throughput of older devices that are not on
> > displaylink connections?
> > 
> > What devices did you test this on, and what is the actual performance
> > changes?  You offer no real information here at all, and large buffer
> > sizes does have other downsides, so determining how you tested this is
> > key.
> > 
> > Also, please wrap your changelogs at 72 columns like git asks you to do.
> > 
> > thanks,
> > 
> > greg k-h
> 
> Hi Greg,
> To my best knowledge that patch should not affect other devices because:
>  - tx,rx buffers size is initialized to 16kb with CDC_NCM_NTB_DEF_SIZE_RX,
> and CDC_NCM_NTB_DEF_SIZE_TX
>    So all existing devices should not be affected by default.
>  - In order to change tx and rx buffer max size you need to additionally
> modify cdc_ncm/tx_max and cdc_ncm/rx_max parameters. This can be done with
> udev rules and ethtool. So if you want to use higher buffer sizes you need
> to specially request that.
> For DisplayLink devices this will be done with udev rule that will be
> installed with other DisplayLink drivers.
>   - This tx,rx buffer sizes are always capped to dwNtbMaxInMaxSize and
> dwNtbMaxOutMaxSize that are advertised by the device itself. So in theory
> that values should be acceptable by the device.
> 
> Here is summary of my tests I have done on such devices:
>  - DisplayLink DL-3xxx family device
>  - DisplayLink DL-6xxx family device
>  - ASUS USB-C2500 2.5G USB3 eth adapter
>  - Plugable USB3 1G USB3 adapter
>  - EDIMAX EU-4307 USB-C adapter
>  - Dell DBQBCBC064 USB-C adapter
> 
> Unfortunately I was not able to find more or older than USB-3 device on
> company's shelf.
> 
> I was doing measurements with:
>  - iperf3 between two linux boxes
>  - http://openspeedtest.com/ instance running on local testing machine
> 
> I can provide you with detailed results, but I think they are quite verbose
> so I will stay with some high level results:
> 
> - All except one from third party usb adapters were not affected by
> increased buffer size. (I have forced them to use tx,rx size as big as their
> advertised dwNtbOutMaxSize and dwNtbInMaxSize).
>   They were generally reaching 912 - 940Mbps (download/upload)
>   Only Edimax adapter experienced decreased download size from 929Mbps to
> 827 with iper3. In openspeedtest this was decrease from 968Mbps to 886Mbps
> 
> - DisplayLink DL-3xxx family devices experienced increase of performance
>   Iperf3:
>    Download from (300Mbps to 870Mbps), also from historical measurements
> on other setup this was (90Mbps to 500Mbps)
>    Upload from 782Mbps to 844Mbps
>   Openspeedtest:
>    Download from 556Mbps to 873Mbps
>    Upload from 727Mbps to 973Mbps
> 
> - DiplayLink DL-6xxx family devices are not affected greatly by buffer size.
> It is more affected by patch enabling ZLP which prevents device from
> temporary network dropouts when playing video from web and network traffic
> going through it is high.

Lots of this information needs to go into the changelog text so that we
understand how you tested this, what you tested this on, and why you are
making this change.

thanks,

greg k-h