net: cdc_ncm: set reasonable padding limits
We pad frames larger than X to maximum size for devices which don't need a ZLP after maximum sized frames. This allows the device to optimize its transfers for one fixed buffer size. X was arbitrarily set at 512 bytes regardless of real buffer maximum, causing extreme overheads due to excessive padding of larger tx buffers. Limit the padding to at most 3 full USB packets, still allowing the overhead to payload ratio of 3/1. Signed-off-by: Bjørn Mork <bjorn@mork.no> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
parent
70559b8970
commit
43e4c6dfc0
|
@ -213,6 +213,10 @@ static void cdc_ncm_update_rxtx_max(struct usbnet *dev, u32 new_rx, u32 new_tx)
|
|||
|
||||
/* max qlen depend on hard_mtu and rx_urb_size */
|
||||
usbnet_update_max_qlen(dev);
|
||||
|
||||
/* never pad more than 3 full USB packets per transfer */
|
||||
ctx->min_tx_pkt = clamp_t(u16, ctx->tx_max - 3 * usb_maxpacket(dev->udev, dev->out, 1),
|
||||
CDC_NCM_MIN_TX_PKT, ctx->tx_max);
|
||||
}
|
||||
|
||||
/* helpers for NCM and MBIM differences */
|
||||
|
@ -947,7 +951,7 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
|
|||
/* variables will be reset at next call */
|
||||
}
|
||||
|
||||
/* If collected data size is less or equal CDC_NCM_MIN_TX_PKT
|
||||
/* If collected data size is less or equal ctx->min_tx_pkt
|
||||
* bytes, we send buffers as it is. If we get more data, it
|
||||
* would be more efficient for USB HS mobile device with DMA
|
||||
* engine to receive a full size NTB, than canceling DMA
|
||||
|
@ -957,7 +961,7 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
|
|||
* a ZLP after full sized NTBs.
|
||||
*/
|
||||
if (!(dev->driver_info->flags & FLAG_SEND_ZLP) &&
|
||||
skb_out->len > CDC_NCM_MIN_TX_PKT)
|
||||
skb_out->len > ctx->min_tx_pkt)
|
||||
memset(skb_put(skb_out, ctx->tx_max - skb_out->len), 0,
|
||||
ctx->tx_max - skb_out->len);
|
||||
else if (skb_out->len < ctx->tx_max && (skb_out->len % dev->maxpacket) == 0)
|
||||
|
|
|
@ -115,6 +115,7 @@ struct cdc_ncm_ctx {
|
|||
u16 tx_seq;
|
||||
u16 rx_seq;
|
||||
u16 connected;
|
||||
u16 min_tx_pkt;
|
||||
};
|
||||
|
||||
u8 cdc_ncm_select_altsetting(struct usb_interface *intf);
|
||||
|
|
Loading…
Reference in a new issue