1 | NAME |
1 | NAME |
2 | IO::AIO - Asynchronous Input/Output |
2 | IO::AIO - Asynchronous Input/Output |
3 | |
3 | |
4 | SYNOPSIS |
4 | SYNOPSIS |
5 | use IO::AIO; |
5 | use IO::AIO; |
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6 | |
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7 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
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8 | my ($fh) = @_; |
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9 | ... |
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10 | }; |
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11 | |
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12 | aio_unlink "/tmp/file", sub { }; |
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13 | |
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14 | aio_read $fh, 30000, 1024, $buffer, 0, sub { |
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15 | $_[0] > 0 or die "read error: $!"; |
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16 | }; |
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17 | |
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18 | # Event |
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19 | Event->io (fd => IO::AIO::poll_fileno, |
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20 | poll => 'r', |
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21 | cb => \&IO::AIO::poll_cb); |
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22 | |
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23 | # Glib/Gtk2 |
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24 | add_watch Glib::IO IO::AIO::poll_fileno, |
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25 | in => sub { IO::AIO::poll_cb; 1 }; |
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26 | |
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27 | # Tk |
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28 | Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", |
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29 | readable => \&IO::AIO::poll_cb); |
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30 | |
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31 | # Danga::Socket |
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32 | Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => |
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33 | \&IO::AIO::poll_cb); |
6 | |
34 | |
7 | DESCRIPTION |
35 | DESCRIPTION |
8 | This module implements asynchronous I/O using whatever means your |
36 | This module implements asynchronous I/O using whatever means your |
9 | operating system supports. |
37 | operating system supports. |
10 | |
38 | |
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17 | currently, for example), and they would only support aio_read and |
45 | currently, for example), and they would only support aio_read and |
18 | aio_write, so the remaining functionality would have to be implemented |
46 | aio_write, so the remaining functionality would have to be implemented |
19 | using threads anyway. |
47 | using threads anyway. |
20 | |
48 | |
21 | Although the module will work with in the presence of other threads, it |
49 | Although the module will work with in the presence of other threads, it |
22 | is currently not reentrant, so use appropriate locking yourself. |
50 | is currently not reentrant, so use appropriate locking yourself, always |
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51 | call "poll_cb" from within the same thread, or never call "poll_cb" (or |
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52 | other "aio_" functions) recursively. |
23 | |
53 | |
24 | FUNCTIONS |
54 | FUNCTIONS |
25 | AIO FUNCTIONS |
55 | AIO FUNCTIONS |
26 | All the "aio_*" calls are more or less thin wrappers around the syscall |
56 | All the "aio_*" calls are more or less thin wrappers around the syscall |
27 | with the same name (sans "aio_"). The arguments are similar or |
57 | with the same name (sans "aio_"). The arguments are similar or |
28 | identical, and they all accept an additional $callback argument which |
58 | identical, and they all accept an additional (and optional) $callback |
29 | must be a code reference. This code reference will get called with the |
59 | argument which must be a code reference. This code reference will get |
30 | syscall return code (e.g. most syscalls return -1 on error, unlike perl, |
60 | called with the syscall return code (e.g. most syscalls return -1 on |
31 | which usually delivers "false") as it's sole argument when the given |
61 | error, unlike perl, which usually delivers "false") as it's sole |
32 | syscall has been executed asynchronously. |
62 | argument when the given syscall has been executed asynchronously. |
33 | |
63 | |
34 | All functions that expect a filehandle will also accept a file |
64 | All functions expecting a filehandle keep a copy of the filehandle |
35 | descriptor. |
65 | internally until the request has finished. |
36 | |
66 | |
37 | The filenames you pass to these routines *must* be absolute. The reason |
67 | The pathnames you pass to these routines *must* be absolute and encoded |
38 | is that at the time the request is being executed, the current working |
68 | in byte form. The reason for the former is that at the time the request |
39 | directory could have changed. Alternatively, you can make sure that you |
69 | is being executed, the current working directory could have changed. |
40 | never change the current working directory. |
70 | Alternatively, you can make sure that you never change the current |
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71 | working directory. |
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72 | |
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73 | To encode pathnames to byte form, either make sure you either: a) always |
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74 | pass in filenames you got from outside (command line, readdir etc.), b) |
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75 | are ASCII or ISO 8859-1, c) use the Encode module and encode your |
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76 | pathnames to the locale (or other) encoding in effect in the user |
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77 | environment, d) use Glib::filename_from_unicode on unicode filenames or |
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78 | e) use something else. |
41 | |
79 | |
42 | aio_open $pathname, $flags, $mode, $callback |
80 | aio_open $pathname, $flags, $mode, $callback |
43 | Asynchronously open or create a file and call the callback with a |
81 | Asynchronously open or create a file and call the callback with a |
44 | newly created filehandle for the file. |
82 | newly created filehandle for the file. |
45 | |
83 | |
46 | The pathname passed to "aio_open" must be absolute. See API NOTES, |
84 | The pathname passed to "aio_open" must be absolute. See API NOTES, |
47 | above, for an explanation. |
85 | above, for an explanation. |
48 | |
86 | |
49 | The $mode argument is a bitmask. See the "Fcntl" module for a list. |
87 | The $flags argument is a bitmask. See the "Fcntl" module for a list. |
50 | They are the same as used in "sysopen". |
88 | They are the same as used by "sysopen". |
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89 | |
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90 | Likewise, $mode specifies the mode of the newly created file, if it |
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91 | didn't exist and "O_CREAT" has been given, just like perl's |
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92 | "sysopen", except that it is mandatory (i.e. use 0 if you don't |
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93 | create new files, and 0666 or 0777 if you do). |
51 | |
94 | |
52 | Example: |
95 | Example: |
53 | |
96 | |
54 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
97 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
55 | if ($_[0]) { |
98 | if ($_[0]) { |
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62 | |
105 | |
63 | aio_close $fh, $callback |
106 | aio_close $fh, $callback |
64 | Asynchronously close a file and call the callback with the result |
107 | Asynchronously close a file and call the callback with the result |
65 | code. *WARNING:* although accepted, you should not pass in a perl |
108 | code. *WARNING:* although accepted, you should not pass in a perl |
66 | filehandle here, as perl will likely close the file descriptor |
109 | filehandle here, as perl will likely close the file descriptor |
67 | itself when the filehandle is destroyed. Normally, you can safely |
110 | another time when the filehandle is destroyed. Normally, you can |
68 | call perls "close" or just let filehandles go out of scope. |
111 | safely call perls "close" or just let filehandles go out of scope. |
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112 | |
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113 | This is supposed to be a bug in the API, so that might change. It's |
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114 | therefore best to avoid this function. |
69 | |
115 | |
70 | aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
116 | aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
71 | aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
117 | aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
72 | Reads or writes "length" bytes from the specified "fh" and "offset" |
118 | Reads or writes "length" bytes from the specified "fh" and "offset" |
73 | into the scalar given by "data" and offset "dataoffset" and calls |
119 | into the scalar given by "data" and offset "dataoffset" and calls |
74 | the callback without the actual number of bytes read (or -1 on |
120 | the callback without the actual number of bytes read (or -1 on |
75 | error, just like the syscall). |
121 | error, just like the syscall). |
76 | |
122 | |
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123 | The $data scalar *MUST NOT* be modified in any way while the request |
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124 | is outstanding. Modifying it can result in segfaults or WW3 (if the |
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125 | necessary/optional hardware is installed). |
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126 | |
77 | Example: Read 15 bytes at offset 7 into scalar $buffer, strating at |
127 | Example: Read 15 bytes at offset 7 into scalar $buffer, starting at |
78 | offset 0 within the scalar: |
128 | offset 0 within the scalar: |
79 | |
129 | |
80 | aio_read $fh, 7, 15, $buffer, 0, sub { |
130 | aio_read $fh, 7, 15, $buffer, 0, sub { |
81 | $_[0] >= 0 or die "read error: $!"; |
131 | $_[0] > 0 or die "read error: $!"; |
82 | print "read <$buffer>\n"; |
132 | print "read $_[0] bytes: <$buffer>\n"; |
83 | }; |
133 | }; |
84 | |
134 | |
85 | aio_readahead $fh,$offset,$length, $callback |
135 | aio_readahead $fh,$offset,$length, $callback |
86 | Asynchronously reads the specified byte range into the page cache, |
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87 | using the "readahead" syscall. If that syscall doesn't exist the |
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88 | status will be -1 and $! is set to ENOSYS. |
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89 | |
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90 | readahead() populates the page cache with data from a file so that |
136 | "aio_readahead" populates the page cache with data from a file so |
91 | subsequent reads from that file will not block on disk I/O. The |
137 | that subsequent reads from that file will not block on disk I/O. The |
92 | $offset argument specifies the starting point from which data is to |
138 | $offset argument specifies the starting point from which data is to |
93 | be read and $length specifies the number of bytes to be read. I/O is |
139 | be read and $length specifies the number of bytes to be read. I/O is |
94 | performed in whole pages, so that offset is effectively rounded down |
140 | performed in whole pages, so that offset is effectively rounded down |
95 | to a page boundary and bytes are read up to the next page boundary |
141 | to a page boundary and bytes are read up to the next page boundary |
96 | greater than or equal to (off-set+length). aio_readahead() does not |
142 | greater than or equal to (off-set+length). "aio_readahead" does not |
97 | read beyond the end of the file. The current file offset of the file |
143 | read beyond the end of the file. The current file offset of the file |
98 | is left unchanged. |
144 | is left unchanged. |
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145 | |
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146 | If that syscall doesn't exist (likely if your OS isn't Linux) it |
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147 | will be emulated by simply reading the data, which would have a |
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148 | similar effect. |
99 | |
149 | |
100 | aio_stat $fh_or_path, $callback |
150 | aio_stat $fh_or_path, $callback |
101 | aio_lstat $fh, $callback |
151 | aio_lstat $fh, $callback |
102 | Works like perl's "stat" or "lstat" in void context. The callback |
152 | Works like perl's "stat" or "lstat" in void context. The callback |
103 | will be called after the stat and the results will be available |
153 | will be called after the stat and the results will be available |
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120 | |
170 | |
121 | aio_unlink $pathname, $callback |
171 | aio_unlink $pathname, $callback |
122 | Asynchronously unlink (delete) a file and call the callback with the |
172 | Asynchronously unlink (delete) a file and call the callback with the |
123 | result code. |
173 | result code. |
124 | |
174 | |
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175 | aio_rmdir $pathname, $callback |
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176 | Asynchronously rmdir (delete) a directory and call the callback with |
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177 | the result code. |
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178 | |
125 | aio_fsync $fh, $callback |
179 | aio_fsync $fh, $callback |
126 | Asynchronously call fsync on the given filehandle and call the |
180 | Asynchronously call fsync on the given filehandle and call the |
127 | callback with the fsync result code. |
181 | callback with the fsync result code. |
128 | |
182 | |
129 | aio_fdatasync $fh, $callback |
183 | aio_fdatasync $fh, $callback |
130 | Asynchronously call fdatasync on the given filehandle and call the |
184 | Asynchronously call fdatasync on the given filehandle and call the |
131 | callback with the fdatasync result code. |
185 | callback with the fdatasync result code. |
132 | |
186 | |
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187 | If this call isn't available because your OS lacks it or it couldn't |
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188 | be detected, it will be emulated by calling "fsync" instead. |
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189 | |
133 | SUPPORT FUNCTIONS |
190 | SUPPORT FUNCTIONS |
134 | $fileno = IO::AIO::poll_fileno |
191 | $fileno = IO::AIO::poll_fileno |
135 | Return the *request result pipe filehandle*. This filehandle must be |
192 | Return the *request result pipe file descriptor*. This filehandle |
136 | polled for reading by some mechanism outside this module (e.g. Event |
193 | must be polled for reading by some mechanism outside this module |
137 | or select, see below). If the pipe becomes readable you have to call |
194 | (e.g. Event or select, see below or the SYNOPSIS). If the pipe |
138 | "poll_cb" to check the results. |
195 | becomes readable you have to call "poll_cb" to check the results. |
139 | |
196 | |
140 | See "poll_cb" for an example. |
197 | See "poll_cb" for an example. |
141 | |
198 | |
142 | IO::AIO::poll_cb |
199 | IO::AIO::poll_cb |
143 | Process all outstanding events on the result pipe. You have to call |
200 | Process all outstanding events on the result pipe. You have to call |
144 | this regularly. Returns the number of events processed. Returns |
201 | this regularly. Returns the number of events processed. Returns |
145 | immediately when no events are outstanding. |
202 | immediately when no events are outstanding. |
146 | |
203 | |
147 | You can use Event to multiplex, e.g.: |
204 | Example: Install an Event watcher that automatically calls |
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205 | IO::AIO::poll_cb with high priority: |
148 | |
206 | |
149 | Event->io (fd => IO::AIO::poll_fileno, |
207 | Event->io (fd => IO::AIO::poll_fileno, |
150 | poll => 'r', async => 1, |
208 | poll => 'r', async => 1, |
151 | cb => \&IO::AIO::poll_cb); |
209 | cb => \&IO::AIO::poll_cb); |
152 | |
210 | |
153 | IO::AIO::poll_wait |
211 | IO::AIO::poll_wait |
154 | Wait till the result filehandle becomes ready for reading (simply |
212 | Wait till the result filehandle becomes ready for reading (simply |
155 | does a select on the filehandle. This is useful if you want to |
213 | does a "select" on the filehandle. This is useful if you want to |
156 | synchronously wait for some requests to finish). |
214 | synchronously wait for some requests to finish). |
157 | |
215 | |
158 | See "nreqs" for an example. |
216 | See "nreqs" for an example. |
159 | |
217 | |
160 | IO::AIO::nreqs |
218 | IO::AIO::nreqs |
161 | Returns the number of requests currently outstanding. |
219 | Returns the number of requests currently outstanding (i.e. for which |
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220 | their callback has not been invoked yet). |
162 | |
221 | |
163 | Example: wait till there are no outstanding requests anymore: |
222 | Example: wait till there are no outstanding requests anymore: |
164 | |
223 | |
165 | IO::AIO::poll_wait, IO::AIO::poll_cb |
224 | IO::AIO::poll_wait, IO::AIO::poll_cb |
166 | while IO::AIO::nreqs; |
225 | while IO::AIO::nreqs; |
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226 | |
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227 | IO::AIO::flush |
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228 | Wait till all outstanding AIO requests have been handled. |
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229 | |
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230 | Strictly equivalent to: |
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231 | |
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232 | IO::AIO::poll_wait, IO::AIO::poll_cb |
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233 | while IO::AIO::nreqs; |
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234 | |
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235 | IO::AIO::poll |
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236 | Waits until some requests have been handled. |
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237 | |
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238 | Strictly equivalent to: |
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239 | |
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240 | IO::AIO::poll_wait, IO::AIO::poll_cb |
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241 | if IO::AIO::nreqs; |
167 | |
242 | |
168 | IO::AIO::min_parallel $nthreads |
243 | IO::AIO::min_parallel $nthreads |
169 | Set the minimum number of AIO threads to $nthreads. The default is |
244 | Set the minimum number of AIO threads to $nthreads. The default is |
170 | 1, which means a single asynchronous operation can be done at one |
245 | 1, which means a single asynchronous operation can be done at one |
171 | time (the number of outstanding operations, however, is unlimited). |
246 | time (the number of outstanding operations, however, is unlimited). |
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199 | If you queue up many requests in a loop it it often improves speed |
274 | If you queue up many requests in a loop it it often improves speed |
200 | if you set this to a relatively low number, such as 100. |
275 | if you set this to a relatively low number, such as 100. |
201 | |
276 | |
202 | Under normal circumstances you don't need to call this function. |
277 | Under normal circumstances you don't need to call this function. |
203 | |
278 | |
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279 | FORK BEHAVIOUR |
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280 | Before the fork IO::AIO enters a quiescent state where no requests can |
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281 | be added in other threads and no results will be processed. After the |
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282 | fork the parent simply leaves the quiescent state and continues |
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283 | request/result processing, while the child clears the request/result |
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284 | queue and starts the same number of threads as were in use by the |
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285 | parent. |
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286 | |
204 | SEE ALSO |
287 | SEE ALSO |
205 | Coro, Linux::AIO. |
288 | Coro, Linux::AIO. |
206 | |
289 | |
207 | AUTHOR |
290 | AUTHOR |
208 | Marc Lehmann <schmorp@schmorp.de> |
291 | Marc Lehmann <schmorp@schmorp.de> |