YAMAMOTO Takashi 837e1a72a4 tcp_send_buffered.c: improve tcp write buffering
* Send data chunk-by-chunk
  Note: A stream socket doesn't have atomicity requirement.

* Increase the chance to use full-sized segments

Benchmark numbers in my environment:

* Over ESP32 wifi
* The peer is NetBSD, which has traditional delayed ack TCP
* iperf uses 16384 bytes buffer

---

without this patch,
CONFIG_IOB_NBUFFERS=36
CONFIG_IOB_BUFSIZE=196

does not work.
see https://github.com/apache/incubator-nuttx/pull/2772#discussion_r592820639

---

without this patch,
CONFIG_IOB_NBUFFERS=128
CONFIG_IOB_BUFSIZE=196
```
nsh> iperf -c 192.168.8.1
       IP: 192.168.8.103

 mode=tcp-client sip=192.168.8.103:5001,dip=192.168.8.1:5001, interval=3, time=30

        Interval Bandwidth

   0-   3 sec,  4.11 Mbits/sec
   3-   6 sec,  4.63 Mbits/sec
   6-   9 sec,  4.89 Mbits/sec
   9-  12 sec,  4.63 Mbits/sec
  12-  15 sec,  4.85 Mbits/sec
  15-  18 sec,  4.85 Mbits/sec
  18-  21 sec,  5.02 Mbits/sec
  21-  24 sec,  3.67 Mbits/sec
  24-  27 sec,  4.94 Mbits/sec
  27-  30 sec,  4.81 Mbits/sec
   0-  30 sec,  4.64 Mbits/sec
nsh>
```

---

with this patch,
CONFIG_IOB_NBUFFERS=36
CONFIG_IOB_BUFSIZE=196
```
nsh> iperf -c 192.168.8.1
       IP: 192.168.8.103

 mode=tcp-client sip=192.168.8.103:5001,dip=192.168.8.1:5001, interval=3, time=30

        Interval Bandwidth

   0-   3 sec,  5.33 Mbits/sec
   3-   6 sec,  5.59 Mbits/sec
   6-   9 sec,  5.55 Mbits/sec
   9-  12 sec,  5.59 Mbits/sec
  12-  15 sec,  5.59 Mbits/sec
  15-  18 sec,  5.72 Mbits/sec
  18-  21 sec,  5.68 Mbits/sec
  21-  24 sec,  5.29 Mbits/sec
  24-  27 sec,  4.67 Mbits/sec
  27-  30 sec,  4.50 Mbits/sec
   0-  30 sec,  5.35 Mbits/sec
nsh>
```

---

with this patch,
CONFIG_IOB_NBUFFERS=128
CONFIG_IOB_BUFSIZE=196
```
nsh> iperf -c 192.168.8.1
       IP: 192.168.8.103

 mode=tcp-client sip=192.168.8.103:5001,dip=192.168.8.1:5001, interval=3, time=30

        Interval Bandwidth

   0-   3 sec,  5.51 Mbits/sec
   3-   6 sec,  4.67 Mbits/sec
   6-   9 sec,  4.54 Mbits/sec
   9-  12 sec,  5.42 Mbits/sec
  12-  15 sec,  5.37 Mbits/sec
  15-  18 sec,  5.11 Mbits/sec
  18-  21 sec,  5.07 Mbits/sec
  21-  24 sec,  5.29 Mbits/sec
  24-  27 sec,  5.77 Mbits/sec
  27-  30 sec,  4.63 Mbits/sec
   0-  30 sec,  5.14 Mbits/sec
nsh>
```
2021-03-22 01:12:59 -07:00
..
2021-02-25 11:31:49 -08:00
2021-03-21 21:51:14 +01:00

README
======

Directory Structure
===================

  nuttx/
   |
   `- net/
       |
       +- arp        - Address resolution protocol (IPv4)
       +- bluetooth  - PF_BLUETOOTH socket interface
       +- devif      - Stack/device interface layer
       +- icmp       - Internet Control Message Protocol (IPv4)
       +- icmpv6     - Internet Control Message Protocol (IPv6)
       +- ieee802154 - PF_IEEE802154 socket interface
       +- inet       - PF_INET/PF_INET6 socket interface
       +- ipforward  - IP forwarding logic
       +- local      - Unix domain (local) sockets
       +- mld        - Multicast Listener Discovery (MLD)
       +- neighbor   - Neighbor Discovery Protocol (IPv6)
       +- netdev     - Socket network device interface
       +- netlink    - Netlink IPC socket interface
       +- pkt        - "Raw" packet socket support
       +- sixlowpan  - 6LoWPAN implementation
       +- socket     - BSD socket interface
       +- route      - Routing table support
       +- tcp        - Transmission Control Protocol
       +- udp        - User Datagram Protocol
       +- usrsock    - User socket API for user-space networking stack
       `- utils      - Miscellaneous utility functions

    +-------------------------------------------------------------------++------------------------+
    |                     Application layer                             || usrsock daemon         |
    +-------------------------------------------------------------------++------------------------+
    +-------------------------------------------------------------------++----------------+ +-----+
    |                   Socket layer (socket/)                          || /dev/usrsock   | |     |
    +-------------------------------------------------------------------++----------------+ |     |
    +------------++--------------------------------------------------++-------------------+ |     |
    |  Network   || Protocol stacks (arp, ipv6, icmp, pkt, tcp, udp) || usrsock/          | |     |
    |   Device   |+--------------------------------------------------++-------------------+ |     |
    | Interface  |+------------------------------------++---------------------------------+ |     |
    | (netdev/)  ||  Network Device Interface (devif/) || Utilities                       | |     |
    +------------++------------------------------------++---------------------------------+ |     |
    +----------------------------------------------------------------+                      |     |
    |                    Network Device Drivers                      |                      | HAL |
    +----------------------------------------------------------------+                      +-----+
    +----------------------------------------------------------------+ +--------------------------+
    |                    Networking Hardware                         | |  Hardware TCP/IP Stack   |
    +----------------------------------------------------------------+ +--------------------------+