theory.html

实现了poll/epoll/devpoll等C++封装

<h1>Theory of Operation</h1>
See also <a href="nonblocking.html">Introduction to Nonblocking I/O</a>.

<h2>Flow of Control in the ftp benchmark program</h2>
The basic idea is that main() starts off the test with the following code:
<pre>
    robouser_t::static_init(&sked, arg_filename,
        arg_clientBandwidth, 0.8 * arg_clientBandwidth, 1500, 
        arg_hostname, 21, arg_username, arg_password);

    /* Start the first user */
    robouser_t::static_startUser();
</pre>
and then sits in an infinite loop that looks like this:
<pre>
    for (;;) {
        /* Let the scheduler run the robots that need it */
        sked->runAll(now);
        /* Find out what sockets need attention */
        nfds = robouser_t::prePoll(&pfds[0]);
        poll(pfds, nfds, 50);
        /* Give them the attention they deserve. */
        for (i=0; i&lt;nfds; i++) {
            if (!pfds[i].revents)
                continue;
            robouser_t::handle_io(pfds[i].fd, pfds[i].revents);
        }
    }
</pre>
The fetching of files is initiated the call to robouser_t::static_startUser(), 
which starts the robouser's state machine going by scheduling a first call to 
robouser_t::ftpCmdDone().  The state machine calls ftp_client_pipe_t::get() to
start the file transfer.  Whenever poll() says a packet is ready, main() calls 
robouser_t::static_handle_io(), which calls ftp_client_pipe_t::handle_io(), 
which reads data from the network, hands it to ftp_client_proto_t::giveInput(),
gets output from the protocol module by calling ftp_client_proto_t::getOutput(),
and sends it to the network.  Whenever the ftp client library finishes a command,
it calls robouser_t::ftpCmdDone(), which starts the next ftp command.

<p>
To see the flow of control in action, run the program in 
verbose mode, and note the class and method names at the beginning
of each line.  Here's an excerpt from the command 
<pre>
/bench -n1 -hkrunch -uspanky -pXXXXXX -ftest.dat -t2 -v 
</pre>
showing the events from the start of the test up to the end of the first
file transfer.  (Repetitive sections are omitted, and line numbers have been added.)
<pre>
  1  Option values:
  2   -hkrunch host name of ftp server
  3   -P21 port number of ftp server
  4   -n1 number of users
  5   -t2 length of run (in seconds)
  6   -b3600 desired bandwidth (in bytes per second)
  7   -usparky user name
  8   -pXXXXXX user password
  9   -ftest.dat file to fetch
 10   -m1500 bytes per 'packet'
 11   -v1 verbose mode
 12  Sked::init: Allocating 2048 bytes.
 13  robouser_t::static_init:
 14  robouser0::start:
 15  ftp_client_proto_t::setState: line 135: m_state was 0, now 1
 16  ftp_client_pipe_t::init(0x806c260, 0xbffff9b0, 3600): bytes_per_tick 36
 17  Sked::addClient(0x806c264, 3257788)
 18  Sked::pop: clearing skc 0x806c264 ->skedIndex
 19  robouser0::ftpCmdDone: m_state 1
 20  ftp_client_pipe_t::connect(krunch, 21, 0)
 21  ftp_client_proto_t::setState: line 135: m_state was 0, now 1
 22  ftp_client_pipe_t::init(0x806c260, 0xbffff9b0, 3600): bytes_per_tick 36
 23  ftp_client_pipe_t::init: Waiting for connect to finish, m_cfd 3
 24  robouser0::watchfd 3
 25  fdmap_t::add(fd 3, userid 0)
 26  ftp_client_pipe_t::login(sparky, XXXXXX)
 27  ftp_client_proto_t::login(sparky,XXXXXX)
 28  ftp_client_pipe_t::handle_io(fd 3, ffff8004): state 0
 29  ftp_client_proto_t::getOutput: Sending 'USER sparky'
 30  ftp_client_pipe_t::handle_io fd 3 put 'USER sparky'
 31  robouser0::gotoState: old state 1 cad 1 0 0;  new state 2 cad 1 0 0
 32  robouser_t::static_prePoll: user 0, ndfs 1
 33  main:handling j 0 fd 3 revents 4
 34  fdmap_t::fd2user(fd 3)
 35  robouser0::static_handle_io(fd 3, revents 4):
 36  ftp_client_pipe_t::handle_io(fd 3, 4): state 0
 37  ftp_client_pipe_t::handle_io: Connect cfd 3 succeeded
 38  robouser_t::static_prePoll: user 0, ndfs 1
 39  main:handling j 0 fd 3 revents 1
 40  fdmap_t::fd2user(fd 3)
 41  robouser0::static_handle_io(fd 3, revents 1):
 42  ftp_client_pipe_t::handle_io(fd 3, 1): state 0
 43  ftp_client_pipe_t::handle_io fd 3 got '220 krunch FTP server (Version wu-2.4.2-VR17(1) Mon Apr 19 09:21:53 EDT 1999) ready.'
 44  ftp_client_proto_t::giveInput: state: 1 oReady 0 status 220, ibuf: '220 krunch FTP server (Version wu-2.4.2-VR17(1) Mon Apr 19 09:21:53 EDT 1999) ready.'
 45  ftp_client_proto_t::giveInput: server ok, 220 krunch FTP server (Version wu-2.4.2-VR17(1) Mon Apr 19 09:21:53 EDT 1999) ready.
 46  ftp_client_proto_t::setState: line 179: m_state was 1, now 3
 47  ftp_client_pipe_t::handle_io fd 3 got '331 Password required for sparky.'
 48  ftp_client_proto_t::giveInput: state: 3 oReady 0 status 331, ibuf: '331 Password required for sparky.'
 49  ftp_client_proto_t::setState: line 201: m_state was 3, now 4
 50  ftp_client_proto_t::getOutput: Sending 'PASS XXXXXX'
 51  ftp_client_pipe_t::handle_io fd 3 put 'PASS XXXXXX'
 52  robouser_t::static_prePoll: user 0, ndfs 1
 53  main:handling j 0 fd 3 revents 4
 54  fdmap_t::fd2user(fd 3)
 55  robouser0::static_handle_io(fd 3, revents 4):
 56  ftp_client_pipe_t::handle_io(fd 3, 4): state 0
 57  robouser_t::static_prePoll: user 0, ndfs 1
 58  main:handling j 0 fd 3 revents 1
 59  fdmap_t::fd2user(fd 3)
 60  robouser0::static_handle_io(fd 3, revents 1):
 61  ftp_client_pipe_t::handle_io(fd 3, 1): state 0
 62  ftp_client_pipe_t::handle_io fd 3 got '230-Please read the file README'
 63  ftp_client_proto_t::giveInput: state: 4 oReady 0 status 230, ibuf: '230-Please read the file README'
 64  ftp_client_proto_t::giveInput: multiline reply begins: '230-Please read the file README'
 65  ftp_client_proto_t::giveInput::PASS ok, 230-Please read the file README
 66  ftp_client_proto_t::setState: line 211: m_state was 4, now 5
 67  ftp_client_pipe_t::handle_io:notify_app: status 230, dfd_conn 0, dfd -1
 68  ftp_client_pipe_t::handle_io:notify_app: calling ftpCmdDone(0, 230)
 69  robouser0::ftpCmdDone: m_state 2
 70  robouser0::ftpCmdDone:CONNECTING: connect succeeded, jumping to state 3
 71  robouser0::gotoState: old state 2 cad 1 0 0;  new state 3 cad 0 1 0
 72  robouser0::ftpCmdDone: m_state 3
 73  robouser0::ftpCmdDone:GET: fetching file test.dat
 74  ftp_client_pipe_t::get(test.dat,1)
 75  ftp_client_proto_t::get(test.dat,): requesting port from server
 76  ftp_client_proto_t::callState: line 496: m_state was 5, now 8
 77  ftp_client_pipe_t::handle_io(fd 3, ffff8004): state 1
 78  ftp_client_proto_t::getOutput: Sending 'PASV'
 79  ftp_client_pipe_t::handle_io fd 3 put 'PASV'
 80  robouser0::gotoState: old state 3 cad 0 1 0;  new state 4 cad 0 1 0
 81  1 users
 82  robouser_t::static_prePoll: user 0, ndfs 1
 83  main:handling j 0 fd 3 revents 1
 84  fdmap_t::fd2user(fd 3)
 85  robouser0::static_handle_io(fd 3, revents 1):
 86  ftp_client_pipe_t::handle_io(fd 3, 1): state 1
 87  ftp_client_pipe_t::handle_io fd 3 got '230-  it was last modified on Wed Nov 10 23:21:37 1999 - 53 days ago'
 88  ftp_client_proto_t::giveInput: state: 8 oReady 0 status 230, ibuf: '230-  it was last modified on Wed Nov 10 23:21:37 1999 - 53 days ago'
 89  ftp_client_proto_t::giveInput: multiline reply continues: '230-  it was last modified on Wed Nov 10 23:21:37 1999 - 53 days ago'
 90  ftp_client_pipe_t::handle_io fd 3 got '230 User sparky logged in.'
 91  ftp_client_proto_t::giveInput: state: 8 oReady 0 status 230, ibuf: '230 User sparky logged in.'
 92  ftp_client_proto_t::giveInput: multiline reply ends: '230 User sparky logged in.'
 93  robouser_t::static_prePoll: user 0, ndfs 1
 94  main:handling j 0 fd 3 revents 1
 95  fdmap_t::fd2user(fd 3)
 96  robouser0::static_handle_io(fd 3, revents 1):
 97  ftp_client_pipe_t::handle_io(fd 3, 1): state 1
 98  ftp_client_pipe_t::handle_io fd 3 got '227 Entering Passive Mode (127,0,0,1,58,93)'
 99  ftp_client_proto_t::giveInput: state: 8 oReady 0 status 227, ibuf: '227 Entering Passive Mode (127,0,0,1,58,93)'
100  ftp_client_proto_t::giveInput::PASV ok, 227 Entering Passive Mode (127,0,0,1,58,93)
101  ftp_client_proto_t::returnState: m_state was 8, now 9
102  ftp_client_proto_t::giveInput::PASV: sending RETR
103  ftp_client_proto_t::getOutput: Sending 'RETR test.dat'
104  ftp_client_pipe_t::handle_io fd 3 put 'RETR test.dat'
105  ftp_client_pipe_t::handle_io: isPortReady TRUE, address 127.0.0.1:23866
106  robouser0::watchfd 4
107  fdmap_t::add(fd 4, userid 0)
108  ftp_client_pipe_t::handle_io: socket returns dfd 4
109  robouser_t::static_prePoll: user 0, ndfs 2
110  main:handling j 0 fd 3 revents 4
111  fdmap_t::fd2user(fd 3)
112  robouser0::static_handle_io(fd 3, revents 4):
113  ftp_client_pipe_t::handle_io(fd 3, 4): state 1
114  ftp_client_pipe_t::handle_io: Connect dfd 4 succeeded
115  robouser_t::static_prePoll: user 0, ndfs 2
116  main:handling j 0 fd 3 revents 1
117  fdmap_t::fd2user(fd 3)
118  robouser0::static_handle_io(fd 3, revents 1):
119  ftp_client_pipe_t::handle_io(fd 3, 1): state 1
120  ftp_client_pipe_t::handle_io fd 3 got '150 Opening ASCII mode data connection for test.dat (2135 bytes).'
121  ftp_client_proto_t::giveInput: state: 9 oReady 0 status 150, ibuf: '150 Opening ASCII mode data connection for test.dat (2135 bytes).'
122  ftp_client_proto_t::giveInput::RETR in progress
123  robouser_t::static_prePoll: user 0, ndfs 2
124  main:handling j 1 fd 4 revents 1
125  fdmap_t::fd2user(fd 4)
126  robouser0::static_handle_io(fd 4, revents 1):
127  ftp_client_pipe_t::handle_io(fd 4, 1): state 1
128  ftp_client_pipe_t::handle_io: calling subclass
129  robouser0::handle_data_io: fd 4, revents 1; read 1500 bytes
130  ftp_client_pipe_t::handle_io: dfd 4 read 1500 bytes, won't read again for 41 ticks
131  robouser_t::static_prePoll: user 0, ndfs 2
132  main:handling j 1 fd 4 revents 1
133  fdmap_t::fd2user(fd 4)
134  robouser0::static_handle_io(fd 4, revents 1):
135  ftp_client_pipe_t::handle_io(fd 4, 1): state 1
136  ftp_client_pipe_t::handle_io: dfd 4 still needs to snooze for 41 ticks
137  Sked::addClient(0x806c284, 3257851)
138  ftp_client_pipe_t::handle_io: dfd 4 asleep; revents 1, m_dfd_events 1
139  robouser_t::static_prePoll: user 0, ndfs 2
140  main:handling j 0 fd 3 revents 1
141  fdmap_t::fd2user(fd 3)
142  robouser0::static_handle_io(fd 3, revents 1):
143  ftp_client_pipe_t::handle_io(fd 3, 1): state 2
144  ftp_client_pipe_t::handle_io fd 3 got '226 Transfer complete.'
145  ftp_client_proto_t::giveInput: state: 9 oReady 0 status 226, ibuf: '226 Transfer complete.'
146  ftp_client_proto_t::giveInput::RETR server finished, 226 Transfer complete.
147  ftp_client_proto_t::setState: line 286: m_state was 9, now 5
148  ftp_client_pipe_t::handle_io:notify_app: status 226, dfd_conn 0, dfd 4
149  ftp_client_pipe_t::handle_io:notify_app: status 226, connecting 0, dfd 4, so no notification yet
150  robouser_t::static_prePoll: user 0, ndfs 2
151  Sked::pop: clearing skc 0x806c284 ->skedIndex
152  ftp_client_pipe_t::handle_io(fd 4, 1): state 1
153  ftp_client_pipe_t::handle_io: calling subclass
154  robouser0::handle_data_io: fd 4, revents 1; read 690 bytes
155  ftp_client_pipe_t::handle_io: dfd 4 read 714 bytes, won't read again for 19 ticks
156  robouser_t::static_prePoll: user 0, ndfs 2
157  main:handling j 1 fd 4 revents 10
158  fdmap_t::fd2user(fd 4)
159  robouser0::static_handle_io(fd 4, revents 10):
160  ftp_client_pipe_t::handle_io(fd 4, 10): state 1
161  ftp_client_pipe_t::handle_io: closing dfd 4
162  Sked::delClient: index 0, m_used 0
163  robouser0::unwatchfd 4
164  fdmap_t::del(fd 4)
165  ftp_client_pipe_t::handle_io:notify_app: status 226, dfd_conn 0, dfd -1
166  ftp_client_pipe_t::handle_io:notify_app: calling ftpCmdDone(0, 226)
167  robouser0::ftpCmdDone: m_state 4
168  User0: fetching 2190 bytes took 0.430000 seconds, 5093 bytes per second

</pre>
Eventually, this page will provide a line-by-line analysis of the above trace.
At the moment, you'll have to wade through it yourself, referring to the
source code to see what printed out each line.
<p>
<hr>
<i>Copyright Dan Kegel 1999<br>
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