Re: [PATCH v3 5/6] mwifiex: do not aggregate tcp ack in usb tx aggregation queue

[Brian Norris <briannorris@chromium.org>]

On Fri, May 19, 2017 at 09:06:44AM +0000, Xinming Hu wrote:
> From: Xinming Hu <huxm@marvell.com>
> 
> Tcp ack should be send as soon to avoid throuput drop during receive tcp
> traffic.
> 
> Signed-off-by: Xinming Hu <huxm@marvell.com>
> Signed-off-by: Cathy Luo <cluo@marvell.com>
> Signed-off-by: Ganapathi Bhat <gbhat@marvell.com>
> ---
> v2: same as v1
> v3: avoid to use magic tcp flag (Kalle)
> ---
>  drivers/net/wireless/marvell/mwifiex/11n_aggr.c |  4 ++++
>  drivers/net/wireless/marvell/mwifiex/decl.h     |  1 +
>  drivers/net/wireless/marvell/mwifiex/main.c     | 26 +++++++++++++++++++++++++
>  drivers/net/wireless/marvell/mwifiex/main.h     |  1 +
>  drivers/net/wireless/marvell/mwifiex/usb.c      |  6 ++++--
>  5 files changed, 36 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/marvell/mwifiex/11n_aggr.c b/drivers/net/wireless/marvell/mwifiex/11n_aggr.c
> index e8ffb26..cbf3bc2 100644
> --- a/drivers/net/wireless/marvell/mwifiex/11n_aggr.c
> +++ b/drivers/net/wireless/marvell/mwifiex/11n_aggr.c
> @@ -194,6 +194,10 @@
>  
>  	if (tx_info_src->flags & MWIFIEX_BUF_FLAG_TDLS_PKT)
>  		tx_info_aggr->flags |= MWIFIEX_BUF_FLAG_TDLS_PKT;
> +
> +	if (tx_info_src->flags & MWIFIEX_BUF_FLAG_TCP_ACK)
> +		tx_info_aggr->flags |= MWIFIEX_BUF_FLAG_TCP_ACK;
> +
>  	tx_info_aggr->flags |= MWIFIEX_BUF_FLAG_AGGR_PKT;
>  	skb_aggr->priority = skb_src->priority;
>  	skb_aggr->tstamp = skb_src->tstamp;
> diff --git a/drivers/net/wireless/marvell/mwifiex/decl.h b/drivers/net/wireless/marvell/mwifiex/decl.h
> index 188e4c3..0487420 100644
> --- a/drivers/net/wireless/marvell/mwifiex/decl.h
> +++ b/drivers/net/wireless/marvell/mwifiex/decl.h
> @@ -89,6 +89,7 @@
>  #define MWIFIEX_BUF_FLAG_EAPOL_TX_STATUS   BIT(3)
>  #define MWIFIEX_BUF_FLAG_ACTION_TX_STATUS  BIT(4)
>  #define MWIFIEX_BUF_FLAG_AGGR_PKT          BIT(5)
> +#define MWIFIEX_BUF_FLAG_TCP_ACK           BIT(6)
>  
>  #define MWIFIEX_BRIDGED_PKTS_THR_HIGH      1024
>  #define MWIFIEX_BRIDGED_PKTS_THR_LOW        128
> diff --git a/drivers/net/wireless/marvell/mwifiex/main.c b/drivers/net/wireless/marvell/mwifiex/main.c
> index 2c42191..b7d835c 100644
> --- a/drivers/net/wireless/marvell/mwifiex/main.c
> +++ b/drivers/net/wireless/marvell/mwifiex/main.c
> @@ -851,6 +851,30 @@ struct sk_buff *
>  	return skb;
>  }
>  
> +static bool is_piggyback_tcp_ack(struct sk_buff *skb)
> +{
> +	struct ethhdr *ethh = NULL;
> +	struct iphdr  *iph = NULL;
> +	struct tcphdr *tcph = NULL;
> +
> +	ethh = (struct ethhdr *)skb->data;
> +	if (ntohs(ethh->h_proto) != ETH_P_IP)
> +		return false;

What about IPv6?

Also, what about all the protocols that you're *not* hacking this for?
Is the latency induced by aggregation really that poor?

I'm not really a networking expert here, but this whole patch smells bad
to me.

> +
> +	iph = (struct iphdr *)((u8 *)ethh + sizeof(struct ethhdr));
> +	if (iph->protocol != IPPROTO_TCP)
> +		return false;
> +
> +	tcph = (struct tcphdr *)((u8 *)iph + iph->ihl * 4);
> +	/* Piggyback ack without payload*/
> +	if (tcp_flag_word(tcph) == TCP_FLAG_ACK &&
> +	    ntohs(iph->tot_len) <= (iph->ihl + tcph->doff) * 4) {
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
>  /*
>   * CFG802.11 network device handler for data transmission.
>   */
> @@ -904,6 +928,8 @@ struct sk_buff *
>  	tx_info->bss_num = priv->bss_num;
>  	tx_info->bss_type = priv->bss_type;
>  	tx_info->pkt_len = skb->len;
> +	if (is_piggyback_tcp_ack(skb))
> +		tx_info->flags |= MWIFIEX_BUF_FLAG_TCP_ACK;
>  
>  	multicast = is_multicast_ether_addr(skb->data);
>  
> diff --git a/drivers/net/wireless/marvell/mwifiex/main.h b/drivers/net/wireless/marvell/mwifiex/main.h
> index 1f7e6c3..b0010a9 100644
> --- a/drivers/net/wireless/marvell/mwifiex/main.h
> +++ b/drivers/net/wireless/marvell/mwifiex/main.h
> @@ -49,6 +49,7 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/slab.h>
>  #include <linux/of_irq.h>
> +#include <linux/tcp.h>

I dislike polluting the (driver-global) main.h with #include's that only
are used in one file. Especially when you talk about seemingly
layer-violating TCP hacks. Can you move this to main.c instead?

Brian

>  
>  #include "decl.h"
>  #include "ioctl.h"
> diff --git a/drivers/net/wireless/marvell/mwifiex/usb.c b/drivers/net/wireless/marvell/mwifiex/usb.c
> index f230017..e9c3d43 100644
> --- a/drivers/net/wireless/marvell/mwifiex/usb.c
> +++ b/drivers/net/wireless/marvell/mwifiex/usb.c
> @@ -934,6 +934,7 @@ static int mwifiex_usb_aggr_tx_data(struct mwifiex_adapter *adapter, u8 ep,
>  	struct urb_context *context = NULL;
>  	struct txpd *local_tx_pd =
>  		(struct txpd *)((u8 *)skb->data + adapter->intf_hdr_len);
> +	struct mwifiex_txinfo *tx_info = MWIFIEX_SKB_TXCB(skb);
>  	u8 f_send_aggr_buf = 0;
>  	u8 f_send_cur_buf = 0;
>  	u8 f_precopy_cur_buf = 0;
> @@ -989,8 +990,9 @@ static int mwifiex_usb_aggr_tx_data(struct mwifiex_adapter *adapter, u8 ep,
>  		}
>  	}
>  
> -	if (local_tx_pd->flags & MWIFIEX_TxPD_POWER_MGMT_NULL_PACKET) {
> -		/* Send NULL packet immediately*/
> +	if (local_tx_pd->flags & MWIFIEX_TxPD_POWER_MGMT_NULL_PACKET ||
> +	    tx_info->flags & MWIFIEX_BUF_FLAG_TCP_ACK) {
> +		/* Send NULL data/TCP ACK packet immediately*/
>  		if (f_precopy_cur_buf) {
>  			if (skb_queue_empty(&port->tx_aggr.aggr_list)) {
>  				f_precopy_cur_buf = 0;
> -- 
> 1.9.1
>