cfee8793a7
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@codeaurora.org> Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.