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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Wen Gong <wgong@codeaurora.org>
Cc:     ath10k@lists.infradead.org, linux-wireless@vger.kernel.org
Subject: Re: [PATCH v5 8/8] ath10k: enable napi on RX path for sdio
References: <1567679893-14029-1-git-send-email-wgong@codeaurora.org>
        <1567679893-14029-9-git-send-email-wgong@codeaurora.org>
Date:   Mon, 23 Sep 2019 12:22:22 +0300
In-Reply-To: <1567679893-14029-9-git-send-email-wgong@codeaurora.org> (Wen
        Gong's message of "Thu, 5 Sep 2019 18:38:13 +0800")
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Wen Gong <wgong@codeaurora.org> writes:

> For tcp RX, the quantity of tcp acks to remote is 1/2 of the quantity
> of tcp data from remote, then it will have many small length packets
> on TX path of sdio bus, then it reduce the RX packets's bandwidth of
> tcp.
>
> This patch enable napi on RX path, then the RX packet of tcp will not
> feed to tcp stack immeditely from mac80211 since GRO is enabled by
> default, it will feed to tcp stack after napi complete, if rx bundle
> is enabled, then it will feed to tcp stack one time for each bundle
> of RX. For example, RX bundle size is 32, then tcp stack will receive
> one large length packet, its length is neary 1500*32, then tcp stack
> will send a tcp ack for this large packet, this will reduce the tcp
> acks ratio from 1/2 to 1/32. This results in significant performance
> improvement for tcp RX.
>
> Tcp rx throughout is 240Mbps without this patch, and it arrive 390Mbps
> with this patch. The cpu usage has no obvious difference with and
> without NAPI.
>
> call stack for each RX packet on GRO path:
> (skb length is about 1500 bytes)
>   skb_gro_receive ([kernel.kallsyms])
>   tcp4_gro_receive ([kernel.kallsyms])
>   inet_gro_receive ([kernel.kallsyms])
>   dev_gro_receive ([kernel.kallsyms])
>   napi_gro_receive ([kernel.kallsyms])
>   ieee80211_deliver_skb ([mac80211])
>   ieee80211_rx_handlers ([mac80211])
>   ieee80211_prepare_and_rx_handle ([mac80211])
>   ieee80211_rx_napi ([mac80211])
>   ath10k_htt_rx_proc_rx_ind_hl ([ath10k_core])
>   ath10k_htt_rx_pktlog_completion_handler ([ath10k_core])
>   ath10k_sdio_napi_poll ([ath10k_sdio])
>   net_rx_action ([kernel.kallsyms])
>   softirqentry_text_start ([kernel.kallsyms])
>   do_softirq ([kernel.kallsyms])
>
> call stack for napi complete and send tcp ack from tcp stack:
> (skb length is about 1500*32 bytes)
>  _tcp_ack_snd_check ([kernel.kallsyms])
>  tcp_v4_do_rcv ([kernel.kallsyms])
>  tcp_v4_rcv ([kernel.kallsyms])
>  local_deliver_finish ([kernel.kallsyms])
>  ip_local_deliver ([kernel.kallsyms])
>  ip_rcv_finish ([kernel.kallsyms])
>  ip_rcv ([kernel.kallsyms])
>  netif_receive_skb_core ([kernel.kallsyms])
>  netif_receive_skb_one_core([kernel.kallsyms])
>  netif_receive_skb ([kernel.kallsyms])
>  netif_receive_skb_internal ([kernel.kallsyms])
>  napi_gro_complete ([kernel.kallsyms])
>  napi_gro_flush ([kernel.kallsyms])
>  napi_complete_done ([kernel.kallsyms])
>  ath10k_sdio_napi_poll ([ath10k_sdio])
>  net_rx_action ([kernel.kallsyms])
>  __softirqentry_text_start ([kernel.kallsyms])
>  do_softirq ([kernel.kallsyms])
>
> Tested with QCA6174 SDIO with firmware
> WLAN.RMH.4.4.1-00007-QCARMSWP-1.
>
> Signed-off-by: Wen Gong <wgong@codeaurora.org>

[...]

> --- a/drivers/net/wireless/ath/ath10k/htt_rx.c
> +++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
> @@ -2263,7 +2263,7 @@ static bool ath10k_htt_rx_proc_rx_ind_hl(struct ath10k_htt *htt,
>  	if (mpdu_ranges->mpdu_range_status == HTT_RX_IND_MPDU_STATUS_TKIP_MIC_ERR)
>  		rx_status->flag |= RX_FLAG_MMIC_ERROR;
>  
> -	ieee80211_rx_ni(ar->hw, skb);
> +	ieee80211_rx_napi(ar->hw, NULL, skb, &ar->napi);

Doesn't this break USB?

-- 
Kalle Valo