On Thu, Jul 14, 2022 at 02:02:17PM +0200, Łukasz Spintzyk wrote: > DisplayLink ethernet devices require NTB buffers larger then 32kb > in order to run with highest performance. > > This patch is changing upper limit of the rx and tx buffers. > Those buffers are initialized with CDC_NCM_NTB_DEF_SIZE_RX and > CDC_NCM_NTB_DEF_SIZE_TX which is 16kb so by default no device is > affected by increased limit. > > Rx and tx buffer is increased under two conditions: > - Device need to advertise that it supports higher buffer size in > dwNtbMaxInMaxSize and dwNtbMaxOutMaxSize. > - cdc_ncm/rx_max and cdc_ncm/tx_max driver parameters must be adjusted > with udev rule or ethtool. > > Summary of testing and performance results: > Tests were performed on following devices: > - DisplayLink DL-3xxx family device > - DisplayLink DL-6xxx family device > - ASUS USB-C2500 2.5G USB3 ethernet adapter > - Plugable USB3 1G USB3 ethernet adapter > - EDIMAX EU-4307 USB-C ethernet adapter > - Dell DBQBCBC064 USB-C ethernet adapter > > Performance measurements were done with: > - iperf3 between two linux boxes > - http://openspeedtest.com/ instance running on local test machine > > Insights from tests results: > - All except one from third party usb adapters were not affected by > increased buffer size to their advertised dwNtbOutMaxSize and > dwNtbInMaxSize. > Devices were generally reaching 912-940Mbps both download and upload. > > Only EDIMAX adapter experienced decreased download size from > 929Mbps to 827Mbps with iper3, with openspeedtest decrease was from > 968Mbps to 886Mbps. > > - DisplayLink DL-3xxx family devices experienced performance increase > with iperf3 download from 300Mbps to 870Mbps and > upload from 782Mbps to 844Mbps. > With openspeedtest download increased from 556Mbps to 873Mbps > and upload from 727Mbps to 973Mbps > > - DiplayLink DL-6xxx family devices are not affected by > increased buffer size. > > Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@xxxxxxxxxxxxx> > --- > > v2: > - Information how to change tx,rx buffer size > - Added performance tests results to the commit description. > > > 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 > Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Thanks for the additional information in the changelog text.
