diff options
| author | Bjørn Mork <bjorn@mork.no> | 2014-05-16 21:48:24 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-05-16 22:39:01 -0400 |
| commit | 43e4c6dfc0fd781e68f20caf563a06f5c6ece995 (patch) | |
| tree | a93b3046f1204521f36dba8c57c7ca8e0c3d8d83 /drivers | |
| parent | 70559b8970e52aa9962dc823fd4498af06809544 (diff) | |
| download | linux-43e4c6dfc0fd781e68f20caf563a06f5c6ece995.tar.bz2 | |
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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/net/usb/cdc_ncm.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c index b9b562b9128a..9592d4669435 100644 --- a/drivers/net/usb/cdc_ncm.c +++ b/drivers/net/usb/cdc_ncm.c @@ -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) |