… | |
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3 | IO::AIO - Asynchronous Input/Output |
3 | IO::AIO - Asynchronous Input/Output |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use IO::AIO; |
7 | use IO::AIO; |
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8 | |
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9 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
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10 | my ($fh) = @_; |
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11 | ... |
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12 | }; |
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13 | |
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14 | aio_unlink "/tmp/file", sub { }; |
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15 | |
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16 | aio_read $fh, 30000, 1024, $buffer, 0, sub { |
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17 | $_[0] > 0 or die "read error: $!"; |
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18 | }; |
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19 | |
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20 | # Event |
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21 | Event->io (fd => IO::AIO::poll_fileno, |
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22 | poll => 'r', |
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23 | cb => \&IO::AIO::poll_cb); |
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24 | |
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25 | # Glib/Gtk2 |
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26 | add_watch Glib::IO IO::AIO::poll_fileno, |
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27 | in => sub { IO::AIO::poll_cb; 1 }; |
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28 | |
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29 | # Tk |
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30 | Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", |
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31 | readable => \&IO::AIO::poll_cb); |
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32 | |
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33 | # Danga::Socket |
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34 | Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => |
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35 | \&IO::AIO::poll_cb); |
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36 | |
8 | |
37 | |
9 | =head1 DESCRIPTION |
38 | =head1 DESCRIPTION |
10 | |
39 | |
11 | This module implements asynchronous I/O using whatever means your |
40 | This module implements asynchronous I/O using whatever means your |
12 | operating system supports. |
41 | operating system supports. |
… | |
… | |
19 | not well-supported (Linux doesn't allow them on normal files currently, |
48 | not well-supported (Linux doesn't allow them on normal files currently, |
20 | for example), and they would only support aio_read and aio_write, so the |
49 | for example), and they would only support aio_read and aio_write, so the |
21 | remaining functionality would have to be implemented using threads anyway. |
50 | remaining functionality would have to be implemented using threads anyway. |
22 | |
51 | |
23 | Although the module will work with in the presence of other threads, it is |
52 | Although the module will work with in the presence of other threads, it is |
24 | currently not reentrant, so use appropriate locking yourself. |
53 | currently not reentrant, so use appropriate locking yourself, always call |
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54 | C<poll_cb> from within the same thread, or never call C<poll_cb> (or other |
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55 | C<aio_> functions) recursively. |
25 | |
56 | |
26 | =cut |
57 | =cut |
27 | |
58 | |
28 | package IO::AIO; |
59 | package IO::AIO; |
29 | |
60 | |
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61 | no warnings; |
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62 | |
30 | use base 'Exporter'; |
63 | use base 'Exporter'; |
31 | |
64 | |
32 | use Fcntl (); |
65 | use Fcntl (); |
33 | |
66 | |
34 | BEGIN { |
67 | BEGIN { |
35 | $VERSION = 0.2; |
68 | $VERSION = 1.5; |
36 | |
69 | |
37 | @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink |
70 | @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink |
38 | aio_fsync aio_fdatasync aio_readahead); |
71 | aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead); |
39 | @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); |
72 | @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); |
40 | |
73 | |
41 | require XSLoader; |
74 | require XSLoader; |
42 | XSLoader::load IO::AIO, $VERSION; |
75 | XSLoader::load IO::AIO, $VERSION; |
43 | } |
76 | } |
… | |
… | |
46 | |
79 | |
47 | =head2 AIO FUNCTIONS |
80 | =head2 AIO FUNCTIONS |
48 | |
81 | |
49 | All the C<aio_*> calls are more or less thin wrappers around the syscall |
82 | All the C<aio_*> calls are more or less thin wrappers around the syscall |
50 | with the same name (sans C<aio_>). The arguments are similar or identical, |
83 | with the same name (sans C<aio_>). The arguments are similar or identical, |
51 | and they all accept an additional C<$callback> argument which must be |
84 | and they all accept an additional (and optional) C<$callback> argument |
52 | a code reference. This code reference will get called with the syscall |
85 | which must be a code reference. This code reference will get called with |
53 | return code (e.g. most syscalls return C<-1> on error, unlike perl, which |
86 | the syscall return code (e.g. most syscalls return C<-1> on error, unlike |
54 | usually delivers "false") as it's sole argument when the given syscall has |
87 | perl, which usually delivers "false") as it's sole argument when the given |
55 | been executed asynchronously. |
88 | syscall has been executed asynchronously. |
56 | |
89 | |
57 | All functions that expect a filehandle will also accept a file descriptor. |
90 | All functions expecting a filehandle keep a copy of the filehandle |
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91 | internally until the request has finished. |
58 | |
92 | |
59 | The filenames you pass to these routines I<must> be absolute. The reason |
93 | The pathnames you pass to these routines I<must> be absolute and |
60 | is that at the time the request is being executed, the current working |
94 | encoded in byte form. The reason for the former is that at the time the |
61 | directory could have changed. Alternatively, you can make sure that you |
95 | request is being executed, the current working directory could have |
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96 | changed. Alternatively, you can make sure that you never change the |
62 | never change the current working directory. |
97 | current working directory. |
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98 | |
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99 | To encode pathnames to byte form, either make sure you either: a) |
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100 | always pass in filenames you got from outside (command line, readdir |
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101 | etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode |
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102 | your pathnames to the locale (or other) encoding in effect in the user |
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103 | environment, d) use Glib::filename_from_unicode on unicode filenames or e) |
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104 | use something else. |
63 | |
105 | |
64 | =over 4 |
106 | =over 4 |
65 | |
107 | |
66 | =item aio_open $pathname, $flags, $mode, $callback |
108 | =item aio_open $pathname, $flags, $mode, $callback |
67 | |
109 | |
… | |
… | |
69 | created filehandle for the file. |
111 | created filehandle for the file. |
70 | |
112 | |
71 | The pathname passed to C<aio_open> must be absolute. See API NOTES, above, |
113 | The pathname passed to C<aio_open> must be absolute. See API NOTES, above, |
72 | for an explanation. |
114 | for an explanation. |
73 | |
115 | |
74 | The C<$mode> argument is a bitmask. See the C<Fcntl> module for a |
116 | The C<$flags> argument is a bitmask. See the C<Fcntl> module for a |
75 | list. They are the same as used in C<sysopen>. |
117 | list. They are the same as used by C<sysopen>. |
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118 | |
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119 | Likewise, C<$mode> specifies the mode of the newly created file, if it |
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120 | didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>, |
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121 | except that it is mandatory (i.e. use C<0> if you don't create new files, |
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122 | and C<0666> or C<0777> if you do). |
76 | |
123 | |
77 | Example: |
124 | Example: |
78 | |
125 | |
79 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
126 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
80 | if ($_[0]) { |
127 | if ($_[0]) { |
… | |
… | |
87 | |
134 | |
88 | =item aio_close $fh, $callback |
135 | =item aio_close $fh, $callback |
89 | |
136 | |
90 | Asynchronously close a file and call the callback with the result |
137 | Asynchronously close a file and call the callback with the result |
91 | code. I<WARNING:> although accepted, you should not pass in a perl |
138 | code. I<WARNING:> although accepted, you should not pass in a perl |
92 | filehandle here, as perl will likely close the file descriptor itself when |
139 | filehandle here, as perl will likely close the file descriptor another |
93 | the filehandle is destroyed. Normally, you can safely call perls C<close> |
140 | time when the filehandle is destroyed. Normally, you can safely call perls |
94 | or just let filehandles go out of scope. |
141 | C<close> or just let filehandles go out of scope. |
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142 | |
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143 | This is supposed to be a bug in the API, so that might change. It's |
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144 | therefore best to avoid this function. |
95 | |
145 | |
96 | =item aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
146 | =item aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
97 | |
147 | |
98 | =item aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
148 | =item aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
99 | |
149 | |
100 | Reads or writes C<length> bytes from the specified C<fh> and C<offset> |
150 | Reads or writes C<length> bytes from the specified C<fh> and C<offset> |
101 | into the scalar given by C<data> and offset C<dataoffset> and calls the |
151 | into the scalar given by C<data> and offset C<dataoffset> and calls the |
102 | callback without the actual number of bytes read (or -1 on error, just |
152 | callback without the actual number of bytes read (or -1 on error, just |
103 | like the syscall). |
153 | like the syscall). |
104 | |
154 | |
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155 | The C<$data> scalar I<MUST NOT> be modified in any way while the request |
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156 | is outstanding. Modifying it can result in segfaults or WW3 (if the |
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157 | necessary/optional hardware is installed). |
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158 | |
105 | Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at |
159 | Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at |
106 | offset C<0> within the scalar: |
160 | offset C<0> within the scalar: |
107 | |
161 | |
108 | aio_read $fh, 7, 15, $buffer, 0, sub { |
162 | aio_read $fh, 7, 15, $buffer, 0, sub { |
109 | $_[0] >= 0 or die "read error: $!"; |
163 | $_[0] > 0 or die "read error: $!"; |
110 | print "read <$buffer>\n"; |
164 | print "read $_[0] bytes: <$buffer>\n"; |
111 | }; |
165 | }; |
112 | |
166 | |
113 | =item aio_readahead $fh,$offset,$length, $callback |
167 | =item aio_readahead $fh,$offset,$length, $callback |
114 | |
168 | |
115 | Asynchronously reads the specified byte range into the page cache, using |
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116 | the C<readahead> syscall. If that syscall doesn't exist the status will be |
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117 | C<-1> and C<$!> is set to ENOSYS. |
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118 | |
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119 | readahead() populates the page cache with data from a file so that |
169 | C<aio_readahead> populates the page cache with data from a file so that |
120 | subsequent reads from that file will not block on disk I/O. The C<$offset> |
170 | subsequent reads from that file will not block on disk I/O. The C<$offset> |
121 | argument specifies the starting point from which data is to be read and |
171 | argument specifies the starting point from which data is to be read and |
122 | C<$length> specifies the number of bytes to be read. I/O is performed in |
172 | C<$length> specifies the number of bytes to be read. I/O is performed in |
123 | whole pages, so that offset is effectively rounded down to a page boundary |
173 | whole pages, so that offset is effectively rounded down to a page boundary |
124 | and bytes are read up to the next page boundary greater than or equal to |
174 | and bytes are read up to the next page boundary greater than or equal to |
125 | (off-set+length). aio_readahead() does not read beyond the end of the |
175 | (off-set+length). C<aio_readahead> does not read beyond the end of the |
126 | file. The current file offset of the file is left unchanged. |
176 | file. The current file offset of the file is left unchanged. |
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177 | |
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178 | If that syscall doesn't exist (likely if your OS isn't Linux) it will be |
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179 | emulated by simply reading the data, which would have a similar effect. |
127 | |
180 | |
128 | =item aio_stat $fh_or_path, $callback |
181 | =item aio_stat $fh_or_path, $callback |
129 | |
182 | |
130 | =item aio_lstat $fh, $callback |
183 | =item aio_lstat $fh, $callback |
131 | |
184 | |
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150 | =item aio_unlink $pathname, $callback |
203 | =item aio_unlink $pathname, $callback |
151 | |
204 | |
152 | Asynchronously unlink (delete) a file and call the callback with the |
205 | Asynchronously unlink (delete) a file and call the callback with the |
153 | result code. |
206 | result code. |
154 | |
207 | |
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208 | =item aio_rmdir $pathname, $callback |
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209 | |
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210 | Asynchronously rmdir (delete) a directory and call the callback with the |
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211 | result code. |
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212 | |
155 | =item aio_fsync $fh, $callback |
213 | =item aio_fsync $fh, $callback |
156 | |
214 | |
157 | Asynchronously call fsync on the given filehandle and call the callback |
215 | Asynchronously call fsync on the given filehandle and call the callback |
158 | with the fsync result code. |
216 | with the fsync result code. |
159 | |
217 | |
160 | =item aio_fdatasync $fh, $callback |
218 | =item aio_fdatasync $fh, $callback |
161 | |
219 | |
162 | Asynchronously call fdatasync on the given filehandle and call the |
220 | Asynchronously call fdatasync on the given filehandle and call the |
163 | callback with the fdatasync result code. |
221 | callback with the fdatasync result code. |
164 | |
222 | |
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223 | If this call isn't available because your OS lacks it or it couldn't be |
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224 | detected, it will be emulated by calling C<fsync> instead. |
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225 | |
165 | =back |
226 | =back |
166 | |
227 | |
167 | =head2 SUPPORT FUNCTIONS |
228 | =head2 SUPPORT FUNCTIONS |
168 | |
229 | |
169 | =over 4 |
230 | =over 4 |
170 | |
231 | |
171 | =item $fileno = IO::AIO::poll_fileno |
232 | =item $fileno = IO::AIO::poll_fileno |
172 | |
233 | |
173 | Return the I<request result pipe filehandle>. This filehandle must be |
234 | Return the I<request result pipe file descriptor>. This filehandle must be |
174 | polled for reading by some mechanism outside this module (e.g. Event |
235 | polled for reading by some mechanism outside this module (e.g. Event or |
175 | or select, see below). If the pipe becomes readable you have to call |
236 | select, see below or the SYNOPSIS). If the pipe becomes readable you have |
176 | C<poll_cb> to check the results. |
237 | to call C<poll_cb> to check the results. |
177 | |
238 | |
178 | See C<poll_cb> for an example. |
239 | See C<poll_cb> for an example. |
179 | |
240 | |
180 | =item IO::AIO::poll_cb |
241 | =item IO::AIO::poll_cb |
181 | |
242 | |
182 | Process all outstanding events on the result pipe. You have to call this |
243 | Process all outstanding events on the result pipe. You have to call this |
183 | regularly. Returns the number of events processed. Returns immediately |
244 | regularly. Returns the number of events processed. Returns immediately |
184 | when no events are outstanding. |
245 | when no events are outstanding. |
185 | |
246 | |
186 | You can use Event to multiplex, e.g.: |
247 | Example: Install an Event watcher that automatically calls |
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248 | IO::AIO::poll_cb with high priority: |
187 | |
249 | |
188 | Event->io (fd => IO::AIO::poll_fileno, |
250 | Event->io (fd => IO::AIO::poll_fileno, |
189 | poll => 'r', async => 1, |
251 | poll => 'r', async => 1, |
190 | cb => \&IO::AIO::poll_cb); |
252 | cb => \&IO::AIO::poll_cb); |
191 | |
253 | |
192 | =item IO::AIO::poll_wait |
254 | =item IO::AIO::poll_wait |
193 | |
255 | |
194 | Wait till the result filehandle becomes ready for reading (simply does a |
256 | Wait till the result filehandle becomes ready for reading (simply does a |
195 | select on the filehandle. This is useful if you want to synchronously wait |
257 | C<select> on the filehandle. This is useful if you want to synchronously wait |
196 | for some requests to finish). |
258 | for some requests to finish). |
197 | |
259 | |
198 | See C<nreqs> for an example. |
260 | See C<nreqs> for an example. |
199 | |
261 | |
200 | =item IO::AIO::nreqs |
262 | =item IO::AIO::nreqs |
201 | |
263 | |
202 | Returns the number of requests currently outstanding. |
264 | Returns the number of requests currently outstanding (i.e. for which their |
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265 | callback has not been invoked yet). |
203 | |
266 | |
204 | Example: wait till there are no outstanding requests anymore: |
267 | Example: wait till there are no outstanding requests anymore: |
205 | |
268 | |
206 | IO::AIO::poll_wait, IO::AIO::poll_cb |
269 | IO::AIO::poll_wait, IO::AIO::poll_cb |
207 | while IO::AIO::nreqs; |
270 | while IO::AIO::nreqs; |
208 | |
271 | |
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272 | =item IO::AIO::flush |
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273 | |
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274 | Wait till all outstanding AIO requests have been handled. |
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275 | |
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276 | Strictly equivalent to: |
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277 | |
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278 | IO::AIO::poll_wait, IO::AIO::poll_cb |
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279 | while IO::AIO::nreqs; |
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280 | |
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281 | =item IO::AIO::poll |
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282 | |
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283 | Waits until some requests have been handled. |
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284 | |
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285 | Strictly equivalent to: |
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286 | |
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287 | IO::AIO::poll_wait, IO::AIO::poll_cb |
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288 | if IO::AIO::nreqs; |
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289 | |
209 | =item IO::AIO::min_parallel $nthreads |
290 | =item IO::AIO::min_parallel $nthreads |
210 | |
291 | |
211 | Set the minimum number of AIO threads to C<$nthreads>. The default is |
292 | Set the minimum number of AIO threads to C<$nthreads>. The current default |
212 | C<1>, which means a single asynchronous operation can be done at one time |
293 | is C<4>, which means four asynchronous operations can be done at one time |
213 | (the number of outstanding operations, however, is unlimited). |
294 | (the number of outstanding operations, however, is unlimited). |
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295 | |
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296 | IO::AIO starts threads only on demand, when an AIO request is queued and |
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297 | no free thread exists. |
214 | |
298 | |
215 | It is recommended to keep the number of threads low, as some Linux |
299 | It is recommended to keep the number of threads low, as some Linux |
216 | kernel versions will scale negatively with the number of threads (higher |
300 | kernel versions will scale negatively with the number of threads (higher |
217 | parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 |
301 | parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 |
218 | threads should be fine. |
302 | threads should be fine. |
219 | |
303 | |
220 | Under normal circumstances you don't need to call this function, as this |
304 | Under most circumstances you don't need to call this function, as the |
221 | module automatically starts some threads (the exact number might change, |
305 | module selects a default that is suitable for low to moderate load. |
222 | and is currently 4). |
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223 | |
306 | |
224 | =item IO::AIO::max_parallel $nthreads |
307 | =item IO::AIO::max_parallel $nthreads |
225 | |
308 | |
226 | Sets the maximum number of AIO threads to C<$nthreads>. If more than |
309 | Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
227 | the specified number of threads are currently running, kill them. This |
310 | specified number of threads are currently running, this function kills |
228 | function blocks until the limit is reached. |
311 | them. This function blocks until the limit is reached. |
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312 | |
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313 | While C<$nthreads> are zero, aio requests get queued but not executed |
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314 | until the number of threads has been increased again. |
229 | |
315 | |
230 | This module automatically runs C<max_parallel 0> at program end, to ensure |
316 | This module automatically runs C<max_parallel 0> at program end, to ensure |
231 | that all threads are killed and that there are no outstanding requests. |
317 | that all threads are killed and that there are no outstanding requests. |
232 | |
318 | |
233 | Under normal circumstances you don't need to call this function. |
319 | Under normal circumstances you don't need to call this function. |
… | |
… | |
237 | Sets the maximum number of outstanding requests to C<$nreqs>. If you |
323 | Sets the maximum number of outstanding requests to C<$nreqs>. If you |
238 | try to queue up more than this number of requests, the caller will block until |
324 | try to queue up more than this number of requests, the caller will block until |
239 | some requests have been handled. |
325 | some requests have been handled. |
240 | |
326 | |
241 | The default is very large, so normally there is no practical limit. If you |
327 | The default is very large, so normally there is no practical limit. If you |
242 | queue up many requests in a loop it it often improves speed if you set |
328 | queue up many requests in a loop it often improves speed if you set |
243 | this to a relatively low number, such as C<100>. |
329 | this to a relatively low number, such as C<100>. |
244 | |
330 | |
245 | Under normal circumstances you don't need to call this function. |
331 | Under normal circumstances you don't need to call this function. |
246 | |
332 | |
247 | =back |
333 | =back |
… | |
… | |
250 | |
336 | |
251 | # support function to convert a fd into a perl filehandle |
337 | # support function to convert a fd into a perl filehandle |
252 | sub _fd2fh { |
338 | sub _fd2fh { |
253 | return undef if $_[0] < 0; |
339 | return undef if $_[0] < 0; |
254 | |
340 | |
255 | # try to be perl5.6-compatible |
341 | # try to generate nice filehandles |
256 | local *AIO_FH; |
342 | my $sym = "IO::AIO::fd#$_[0]"; |
257 | open AIO_FH, "+<&=$_[0]" |
343 | local *$sym; |
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344 | |
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345 | open *$sym, "+<&=$_[0]" # usually works under any unix |
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346 | or open *$sym, "<&=$_[0]" # cygwin needs this |
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347 | or open *$sym, ">&=$_[0]" # or this |
258 | or return undef; |
348 | or return undef; |
259 | |
349 | |
260 | *AIO_FH |
350 | *$sym |
261 | } |
351 | } |
262 | |
352 | |
263 | min_parallel 4; |
353 | min_parallel 4; |
264 | |
354 | |
265 | END { |
355 | END { |
266 | max_parallel 0; |
356 | max_parallel 0; |
267 | } |
357 | } |
268 | |
358 | |
269 | 1; |
359 | 1; |
270 | |
360 | |
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361 | =head2 FORK BEHAVIOUR |
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362 | |
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363 | Before the fork, IO::AIO enters a quiescent state where no requests |
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364 | can be added in other threads and no results will be processed. After |
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365 | the fork the parent simply leaves the quiescent state and continues |
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366 | request/result processing, while the child clears the request/result |
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367 | queue (so the requests started before the fork will only be handled in |
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368 | the parent). Threats will be started on demand until the limit ste in the |
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369 | parent process has been reached again. |
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370 | |
271 | =head1 SEE ALSO |
371 | =head1 SEE ALSO |
272 | |
372 | |
273 | L<Coro>, L<Linux::AIO>. |
373 | L<Coro>, L<Linux::AIO>. |
274 | |
374 | |
275 | =head1 AUTHOR |
375 | =head1 AUTHOR |