Wen Gong <wgong@xxxxxxxxxxxxxx> 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.4.4.1-00017-QCARMSWP-1.
>
> Signed-off-by: Wen Gong <wgong@xxxxxxxxxxxxxx>
[...]
> +void ath10k_sdio_init_napi(struct ath10k *ar)
> +{
> + netif_napi_add(&ar->napi_dev, &ar->napi, ath10k_sdio_napi_poll,
> + ATH10K_NAPI_BUDGET);
> +}
This had a new warning:
drivers/net/wireless/ath/ath10k/sdio.c:2053:6: warning: no previous prototype for 'ath10k_sdio_init_napi' [-Wmissing-prototypes]
drivers/net/wireless/ath/ath10k/sdio.c:2053:6: warning: symbol 'ath10k_sdio_init_napi' was not declared. Should it be static?
But as you are calling this function from only ath10k_sdio_probe(), in
the pending branch I removed the function and moved the napi call there.
--
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
