| Message ID | 20200806161643.1694266-1-lorenzo@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | usb: gadget: u_ether: enable qmult on SuperSpeed Plus as well | expand |
On Thu, Aug 6, 2020 at 9:17 AM Lorenzo Colitti <lorenzo@google.com> wrote: > > The u_ether driver has a qmult setting that multiplies the > transmit queue length (which by default is 2). > > The intent is that it should be enabled at high/super speed, but > because the code does not explicitly check for USB_SUPER_PLUS, > it is disabled at that speed. > > Fix this by ensuring that the queue multiplier is enabled for any > wired link at high speed or above. Using >= for USB_SPEED_* > constants seems correct because it is what the gadget_is_xxxspeed > functions do. > > The queue multiplier substantially helps performance at higher > speeds. On a direct SuperSpeed Plus link to a Linux laptop, > iperf3 single TCP stream: > > Before (qmult=1): 1.3 Gbps > After (qmult=5): 3.2 Gbps > > Signed-off-by: Lorenzo Colitti <lorenzo@google.com> > --- > drivers/usb/gadget/function/u_ether.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c > index c3cc6bd14e..31ea76adcc 100644 > --- a/drivers/usb/gadget/function/u_ether.c > +++ b/drivers/usb/gadget/function/u_ether.c > @@ -93,7 +93,7 @@ struct eth_dev { > static inline int qlen(struct usb_gadget *gadget, unsigned qmult) > { > if (gadget_is_dualspeed(gadget) && (gadget->speed == USB_SPEED_HIGH || > - gadget->speed == USB_SPEED_SUPER)) > + gadget->speed >= USB_SPEED_SUPER)) > return qmult * DEFAULT_QLEN; > else > return DEFAULT_QLEN; > -- > 2.28.0.163.g6104cc2f0b6-goog > Reviewed-by: Maciej Żenczykowski <maze@google.com> Though I think this probably deserves a fixes tag of some sort. Probably: Fixes: 04617db7aa68 ("usb: gadget: add SS descriptors to Ethernet gadget") since that's the commit that did: -MODULE_PARM_DESC(qmult, "queue length multiplier at high speed"); +MODULE_PARM_DESC(qmult, "queue length multiplier at high/super speed"); ... -/* for dual-speed hardware, use deeper queues at highspeed */ +/* for dual-speed hardware, use deeper queues at high/super speed */ static inline int qlen(struct usb_gadget *gadget) { - if (gadget_is_dualspeed(gadget) && gadget->speed == USB_SPEED_HIGH) + if (gadget_is_dualspeed(gadget) && (gadget->speed == USB_SPEED_HIGH || + gadget->speed == USB_SPEED_SUPER)) return qmult * DEFAULT_QLEN; else return DEFAULT_QLEN;
btw. it looks like irq throttling in the same file:
@@ -598,9 +599,10 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
- /* throttle highspeed IRQ rate back slightly */
+ /* throttle high/super speed IRQ rate back slightly */
if (gadget_is_dualspeed(dev->gadget))
- req->no_interrupt = (dev->gadget->speed == USB_SPEED_HIGH)
+ req->no_interrupt = (dev->gadget->speed == USB_SPEED_HIGH ||
+ dev->gadget->speed == USB_SPEED_SUPER)
should also be fixed to be >= SUPER and not ==.
On Thu, Aug 6, 2020 at 10:29 AM Maciej Żenczykowski
<zenczykowski@gmail.com> wrote:
>
> On Thu, Aug 6, 2020 at 9:17 AM Lorenzo Colitti <lorenzo@google.com> wrote:
> >
> > The u_ether driver has a qmult setting that multiplies the
> > transmit queue length (which by default is 2).
> >
> > The intent is that it should be enabled at high/super speed, but
> > because the code does not explicitly check for USB_SUPER_PLUS,
> > it is disabled at that speed.
> >
> > Fix this by ensuring that the queue multiplier is enabled for any
> > wired link at high speed or above. Using >= for USB_SPEED_*
> > constants seems correct because it is what the gadget_is_xxxspeed
> > functions do.
> >
> > The queue multiplier substantially helps performance at higher
> > speeds. On a direct SuperSpeed Plus link to a Linux laptop,
> > iperf3 single TCP stream:
> >
> > Before (qmult=1): 1.3 Gbps
> > After (qmult=5): 3.2 Gbps
> >
> > Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
> > ---
> > drivers/usb/gadget/function/u_ether.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
> > index c3cc6bd14e..31ea76adcc 100644
> > --- a/drivers/usb/gadget/function/u_ether.c
> > +++ b/drivers/usb/gadget/function/u_ether.c
> > @@ -93,7 +93,7 @@ struct eth_dev {
> > static inline int qlen(struct usb_gadget *gadget, unsigned qmult)
> > {
> > if (gadget_is_dualspeed(gadget) && (gadget->speed == USB_SPEED_HIGH ||
> > - gadget->speed == USB_SPEED_SUPER))
> > + gadget->speed >= USB_SPEED_SUPER))
> > return qmult * DEFAULT_QLEN;
> > else
> > return DEFAULT_QLEN;
> > --
> > 2.28.0.163.g6104cc2f0b6-goog
> >
>
> Reviewed-by: Maciej Żenczykowski <maze@google.com>
>
> Though I think this probably deserves a fixes tag of some sort.
> Probably:
>
> Fixes: 04617db7aa68 ("usb: gadget: add SS descriptors to Ethernet gadget")
>
> since that's the commit that did:
>
> -MODULE_PARM_DESC(qmult, "queue length multiplier at high speed");
> +MODULE_PARM_DESC(qmult, "queue length multiplier at high/super speed");
>
> ...
>
> -/* for dual-speed hardware, use deeper queues at highspeed */
> +/* for dual-speed hardware, use deeper queues at high/super speed */
> static inline int qlen(struct usb_gadget *gadget)
> {
> - if (gadget_is_dualspeed(gadget) && gadget->speed == USB_SPEED_HIGH)
> + if (gadget_is_dualspeed(gadget) && (gadget->speed == USB_SPEED_HIGH ||
> + gadget->speed == USB_SPEED_SUPER))
> return qmult * DEFAULT_QLEN;
> else
> return DEFAULT_QLEN;
> Reviewed-by: Maciej Żenczykowski <maze@google.com> > > Though I think this probably deserves a fixes tag of some sort. > Probably: > > Fixes: 04617db7aa68 ("usb: gadget: add SS descriptors to Ethernet gadget") > > since that's the commit that did: > > -MODULE_PARM_DESC(qmult, "queue length multiplier at high speed"); > +MODULE_PARM_DESC(qmult, "queue length multiplier at high/super speed"); Thanks for the review. Added Fixes: tag in v2.
On Fri, Aug 7, 2020 at 2:41 AM Maciej Żenczykowski <zenczykowski@gmail.com> wrote: > btw. it looks like irq throttling in the same file: > > @@ -598,9 +599,10 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb, > - /* throttle highspeed IRQ rate back slightly */ > + /* throttle high/super speed IRQ rate back slightly */ > if (gadget_is_dualspeed(dev->gadget)) > - req->no_interrupt = (dev->gadget->speed == USB_SPEED_HIGH) > + req->no_interrupt = (dev->gadget->speed == USB_SPEED_HIGH || > + dev->gadget->speed == USB_SPEED_SUPER) > > should also be fixed to be >= SUPER and not ==. That code was removed by fd9afd3cbe40 ("usb: gadget: u_ether: remove interrupt throttling").
diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c index c3cc6bd14e..31ea76adcc 100644 --- a/drivers/usb/gadget/function/u_ether.c +++ b/drivers/usb/gadget/function/u_ether.c @@ -93,7 +93,7 @@ struct eth_dev { static inline int qlen(struct usb_gadget *gadget, unsigned qmult) { if (gadget_is_dualspeed(gadget) && (gadget->speed == USB_SPEED_HIGH || - gadget->speed == USB_SPEED_SUPER)) + gadget->speed >= USB_SPEED_SUPER)) return qmult * DEFAULT_QLEN; else return DEFAULT_QLEN;
The u_ether driver has a qmult setting that multiplies the transmit queue length (which by default is 2). The intent is that it should be enabled at high/super speed, but because the code does not explicitly check for USB_SUPER_PLUS, it is disabled at that speed. Fix this by ensuring that the queue multiplier is enabled for any wired link at high speed or above. Using >= for USB_SPEED_* constants seems correct because it is what the gadget_is_xxxspeed functions do. The queue multiplier substantially helps performance at higher speeds. On a direct SuperSpeed Plus link to a Linux laptop, iperf3 single TCP stream: Before (qmult=1): 1.3 Gbps After (qmult=5): 3.2 Gbps Signed-off-by: Lorenzo Colitti <lorenzo@google.com> --- drivers/usb/gadget/function/u_ether.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)