On Thu, Apr 11, 2013 at 10:40 PM, Ming Lei <ming.lei@xxxxxxxxxxxxx> wrote:
> The link change is detected via the interrupt pipe, and bulk
> pipes are responsible for transfering packets, so it is reasonable
> to stop bulk transfer after link is reported as off.
>
> Two adavantages may be obtained with stopping bulk transfer
> after link becomes off:
>
> - USB bus bandwidth is saved(USB bus is shared bus except for
> USB3.0), for example, lots of 'IN' token packets and 'NYET'
> handshake packets is transfered on 2.0 bus.
>
> - probabaly power might be saved for usb host controller since
> cancelling bulk transfer may disable the asynchronous schedule of
> host controller.
>
> With this patch, when link becomes off, about ~10% performance
> boost can be found on bulk transfer of anther usb device which
> is attached to same bus with the usbnet device, see below
> test on next-20130410:
>
> - read from usb mass storage(Sandisk Extreme USB 3.0) on pandaboard
> with below command after unplugging ethernet cable:
>
> dd if=/dev/sda iflag=direct of=/dev/null bs=1M count=500
Sorry, the above should be:
dd if=/dev/sda iflag=direct of=/dev/null bs=1M count=800
>
> - without the patch
> 1, 838860800 bytes (839 MB) copied, 36.2216 s, 23.2 MB/s
> 2, 838860800 bytes (839 MB) copied, 35.8368 s, 23.4 MB/s
> 3, 838860800 bytes (839 MB) copied, 35.823 s, 23.4 MB/s
> 4, 838860800 bytes (839 MB) copied, 35.937 s, 23.3 MB/s
> 5, 838860800 bytes (839 MB) copied, 35.7365 s, 23.5 MB/s
> average: 23.6MB/s
>
> - with the patch
> 1, 838860800 bytes (839 MB) copied, 32.3817 s, 25.9 MB/s
> 2, 838860800 bytes (839 MB) copied, 31.7389 s, 26.4 MB/s
> 3, 838860800 bytes (839 MB) copied, 32.438 s, 25.9 MB/s
> 4, 838860800 bytes (839 MB) copied, 32.5492 s, 25.8 MB/s
> 5, 838860800 bytes (839 MB) copied, 31.6178 s, 26.5 MB/s
> average: 26.1MB/s
>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
> ---
> drivers/net/usb/usbnet.c | 30 ++++++++++++++++++++++++++++++
> include/linux/usb/usbnet.h | 1 +
> 2 files changed, 31 insertions(+)
>
> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
> index 34e4252..1e5a9b7 100644
> --- a/drivers/net/usb/usbnet.c
> +++ b/drivers/net/usb/usbnet.c
> @@ -938,6 +938,27 @@ static const struct ethtool_ops usbnet_ethtool_ops = {
>
> /*-------------------------------------------------------------------------*/
>
> +static void __handle_link_change(struct usbnet *dev)
> +{
> + if (!test_bit(EVENT_DEV_OPEN, &dev->flags))
> + return;
> +
> + if (!netif_carrier_ok(dev->net)) {
> + /* kill URBs for reading packets to save bus bandwidth */
> + unlink_urbs(dev, &dev->rxq);
> +
> + /*
> + * tx_timeout will unlink URBs for sending packets and
> + * tx queue is stopped by netcore after link becomes off
> + */
> + } else {
> + /* submitting URBs for reading packets */
> + tasklet_schedule(&dev->bh);
> + }
> +
> + clear_bit(EVENT_LINK_CHANGE, &dev->flags);
> +}
> +
> /* work that cannot be done in interrupt context uses keventd.
> *
> * NOTE: with 2.5 we could do more of this using completion callbacks,
> @@ -1035,8 +1056,14 @@ skip_reset:
> } else {
> usb_autopm_put_interface(dev->intf);
> }
> +
> + /* handle link change from link resetting */
> + __handle_link_change(dev);
> }
>
> + if (test_bit (EVENT_LINK_CHANGE, &dev->flags))
> + __handle_link_change(dev);
> +
> if (dev->flags)
> netdev_dbg(dev->net, "kevent done, flags = 0x%lx\n", dev->flags);
> }
> @@ -1286,6 +1313,7 @@ static void usbnet_bh (unsigned long param)
> // or are we maybe short a few urbs?
> } else if (netif_running (dev->net) &&
> netif_device_present (dev->net) &&
> + netif_carrier_ok(dev->net) &&
> !timer_pending (&dev->delay) &&
> !test_bit (EVENT_RX_HALT, &dev->flags)) {
> int temp = dev->rxq.qlen;
> @@ -1663,6 +1691,8 @@ void usbnet_link_change(struct usbnet *dev, bool link, bool need_reset)
>
> if (need_reset && link)
> usbnet_defer_kevent(dev, EVENT_LINK_RESET);
> + else
> + usbnet_defer_kevent(dev, EVENT_LINK_CHANGE);
> }
> EXPORT_SYMBOL(usbnet_link_change);
>
> diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
> index eb021b8..da46327 100644
> --- a/include/linux/usb/usbnet.h
> +++ b/include/linux/usb/usbnet.h
> @@ -72,6 +72,7 @@ struct usbnet {
> # define EVENT_DEVICE_REPORT_IDLE 8
> # define EVENT_NO_RUNTIME_PM 9
> # define EVENT_RX_KILL 10
> +# define EVENT_LINK_CHANGE 11
> };
>
> static inline struct usb_driver *driver_of(struct usb_interface *intf)
> --
> 1.7.9.5
>
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