From 43e4c6dfc0fd781e68f20caf563a06f5c6ece995 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Bj=C3=B8rn=20Mork?= Date: Fri, 16 May 2014 21:48:24 +0200 Subject: [PATCH] net: cdc_ncm: set reasonable padding limits MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: David S. Miller --- drivers/net/usb/cdc_ncm.c | 8 ++++++-- include/linux/usb/cdc_ncm.h | 1 + 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c index b9b562b..9592d46 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) diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h index 60a44b8..79de672 100644 --- a/include/linux/usb/cdc_ncm.h +++ b/include/linux/usb/cdc_ncm.h @@ -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); -- 2.7.4