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Date: Fri, 2 May 2014 23:11:54 +0200 From: Bjørn Mork <bjorn@...k.no> To: netdev@...r.kernel.org Cc: linux-usb@...r.kernel.org, Alexey Orishko <alexey.orishko@...il.com>, Oliver Neukum <oliver@...kum.org>, Bjørn Mork <bjorn@...k.no> Subject: [RFC 7/9] 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@...k.no> --- 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 faa494c0377e..e28b530bff3a 100644 --- a/drivers/net/usb/cdc_ncm.c +++ b/drivers/net/usb/cdc_ncm.c @@ -201,6 +201,10 @@ 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 */ @@ -936,7 +940,7 @@ 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 @@ -946,7 +950,7 @@ 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 % dev->maxpacket) == 0) diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h index bbc4ce9ffef5..0aac70ee23b6 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 usbnet *dev, struct usb_interface *intf); -- 2.0.0.rc0 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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