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 | |
… | |
… | |
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. |
23 | |
51 | |
24 | API NOTES |
52 | FUNCTIONS |
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53 | AIO FUNCTIONS |
25 | All the "aio_*" calls are more or less thin wrappers around the syscall |
54 | All the "aio_*" calls are more or less thin wrappers around the syscall |
26 | with the same name (sans "aio_"). The arguments are similar or |
55 | with the same name (sans "aio_"). The arguments are similar or |
27 | identical, and they all accept an additional $callback argument which |
56 | identical, and they all accept an additional (and optional) $callback |
28 | must be a code reference. This code reference will get called with the |
57 | argument which must be a code reference. This code reference will get |
29 | syscall return code (e.g. most syscalls return -1 on error, unlike perl, |
58 | called with the syscall return code (e.g. most syscalls return -1 on |
30 | which usually delivers "false") as it's sole argument when the given |
59 | error, unlike perl, which usually delivers "false") as it's sole |
31 | syscall has been executed asynchronously. |
60 | argument when the given syscall has been executed asynchronously. |
32 | |
61 | |
33 | All functions that expect a filehandle will also accept a file |
62 | All functions that expect a filehandle will also accept a file |
34 | descriptor. |
63 | descriptor. |
35 | |
64 | |
36 | The filenames you pass to these routines *must* be absolute. The reason |
65 | The filenames you pass to these routines *must* be absolute. The reason |
37 | is that at the time the request is being executed, the current working |
66 | is that at the time the request is being executed, the current working |
38 | directory could have changed. Alternatively, you can make sure that you |
67 | directory could have changed. Alternatively, you can make sure that you |
39 | never change the current working directory. |
68 | never change the current working directory. |
40 | |
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41 | IO::AIO::min_parallel $nthreads |
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42 | Set the minimum number of AIO threads to $nthreads. The default is |
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43 | 1, which means a single asynchronous operation can be done at one |
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44 | time (the number of outstanding operations, however, is unlimited). |
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45 | |
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46 | It is recommended to keep the number of threads low, as some Linux |
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47 | kernel versions will scale negatively with the number of threads |
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48 | (higher parallelity => MUCH higher latency). With current Linux 2.6 |
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49 | versions, 4-32 threads should be fine. |
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50 | |
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51 | Under normal circumstances you don't need to call this function, as |
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52 | this module automatically starts some threads (the exact number |
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53 | might change, and is currently 4). |
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54 | |
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55 | IO::AIO::max_parallel $nthreads |
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56 | Sets the maximum number of AIO threads to $nthreads. If more than |
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57 | the specified number of threads are currently running, kill them. |
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58 | This function blocks until the limit is reached. |
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59 | |
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60 | This module automatically runs "max_parallel 0" at program end, to |
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61 | ensure that all threads are killed and that there are no outstanding |
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62 | requests. |
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63 | |
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64 | Under normal circumstances you don't need to call this function. |
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65 | |
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66 | $oldnreqs = IO::AIO::max_outstanding $nreqs |
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67 | Sets the maximum number of outstanding requests to $nreqs. If you |
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68 | try to queue up more than this number of requests, the caller will |
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69 | block until some requests have been handled. |
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70 | |
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71 | The default is very large, so normally there is no practical limit. |
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72 | If you queue up many requests in a loop it it often improves speed |
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73 | if you set this to a relatively low number, such as 100. |
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74 | |
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75 | Under normal circumstances you don't need to call this function. |
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76 | |
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77 | $fileno = IO::AIO::poll_fileno |
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78 | Return the *request result pipe filehandle*. This filehandle must be |
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79 | polled for reading by some mechanism outside this module (e.g. Event |
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80 | or select, see below). If the pipe becomes readable you have to call |
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81 | "poll_cb" to check the results. |
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82 | |
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83 | See "poll_cb" for an example. |
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84 | |
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85 | IO::AIO::poll_cb |
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86 | Process all outstanding events on the result pipe. You have to call |
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87 | this regularly. Returns the number of events processed. Returns |
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88 | immediately when no events are outstanding. |
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89 | |
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90 | You can use Event to multiplex, e.g.: |
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91 | |
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92 | Event->io (fd => IO::AIO::poll_fileno, |
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93 | poll => 'r', async => 1, |
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94 | cb => \&IO::AIO::poll_cb); |
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95 | |
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96 | IO::AIO::poll_wait |
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97 | Wait till the result filehandle becomes ready for reading (simply |
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98 | does a select on the filehandle. This is useful if you want to |
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99 | synchronously wait for some requests to finish). |
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100 | |
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101 | See "nreqs" for an example. |
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102 | |
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103 | IO::AIO::nreqs |
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104 | Returns the number of requests currently outstanding. |
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105 | |
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106 | Example: wait till there are no outstanding requests anymore: |
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107 | |
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108 | IO::AIO::poll_wait, IO::AIO::poll_cb |
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109 | while IO::AIO::nreqs; |
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110 | |
69 | |
111 | aio_open $pathname, $flags, $mode, $callback |
70 | aio_open $pathname, $flags, $mode, $callback |
112 | Asynchronously open or create a file and call the callback with a |
71 | Asynchronously open or create a file and call the callback with a |
113 | newly created filehandle for the file. |
72 | newly created filehandle for the file. |
114 | |
73 | |
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141 | Reads or writes "length" bytes from the specified "fh" and "offset" |
100 | Reads or writes "length" bytes from the specified "fh" and "offset" |
142 | into the scalar given by "data" and offset "dataoffset" and calls |
101 | into the scalar given by "data" and offset "dataoffset" and calls |
143 | the callback without the actual number of bytes read (or -1 on |
102 | the callback without the actual number of bytes read (or -1 on |
144 | error, just like the syscall). |
103 | error, just like the syscall). |
145 | |
104 | |
146 | Example: Read 15 bytes at offset 7 into scalar $buffer, strating at |
105 | Example: Read 15 bytes at offset 7 into scalar $buffer, starting at |
147 | offset 0 within the scalar: |
106 | offset 0 within the scalar: |
148 | |
107 | |
149 | aio_read $fh, 7, 15, $buffer, 0, sub { |
108 | aio_read $fh, 7, 15, $buffer, 0, sub { |
150 | $_[0] >= 0 or die "read error: $!"; |
109 | $_[0] > 0 or die "read error: $!"; |
151 | print "read <$buffer>\n"; |
110 | print "read $_[0] bytes: <$buffer>\n"; |
152 | }; |
111 | }; |
153 | |
112 | |
154 | aio_readahead $fh,$offset,$length, $callback |
113 | aio_readahead $fh,$offset,$length, $callback |
155 | Asynchronously reads the specified byte range into the page cache, |
114 | Asynchronously reads the specified byte range into the page cache, |
156 | using the "readahead" syscall. If that syscall doesn't exist the |
115 | using the "readahead" syscall. If that syscall doesn't exist (likely |
157 | status will be -1 and $! is set to ENOSYS. |
116 | if your OS isn't Linux) the status will be -1 and $! is set to |
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117 | ENOSYS. |
158 | |
118 | |
159 | readahead() populates the page cache with data from a file so that |
119 | readahead() populates the page cache with data from a file so that |
160 | subsequent reads from that file will not block on disk I/O. The |
120 | subsequent reads from that file will not block on disk I/O. The |
161 | $offset argument specifies the starting point from which data is to |
121 | $offset argument specifies the starting point from which data is to |
162 | be read and $length specifies the number of bytes to be read. I/O is |
122 | be read and $length specifies the number of bytes to be read. I/O is |
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197 | |
157 | |
198 | aio_fdatasync $fh, $callback |
158 | aio_fdatasync $fh, $callback |
199 | Asynchronously call fdatasync on the given filehandle and call the |
159 | Asynchronously call fdatasync on the given filehandle and call the |
200 | callback with the fdatasync result code. |
160 | callback with the fdatasync result code. |
201 | |
161 | |
202 | BUGS |
162 | SUPPORT FUNCTIONS |
203 | - could be optimized to use more semaphores instead of filehandles. |
163 | $fileno = IO::AIO::poll_fileno |
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164 | Return the *request result pipe filehandle*. This filehandle must be |
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165 | polled for reading by some mechanism outside this module (e.g. Event |
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166 | or select, see below). If the pipe becomes readable you have to call |
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167 | "poll_cb" to check the results. |
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168 | |
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169 | See "poll_cb" for an example. |
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170 | |
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171 | IO::AIO::poll_cb |
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172 | Process all outstanding events on the result pipe. You have to call |
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173 | this regularly. Returns the number of events processed. Returns |
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174 | immediately when no events are outstanding. |
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175 | |
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176 | You can use Event to multiplex, e.g.: |
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177 | |
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178 | Event->io (fd => IO::AIO::poll_fileno, |
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179 | poll => 'r', async => 1, |
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180 | cb => \&IO::AIO::poll_cb); |
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181 | |
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182 | IO::AIO::poll_wait |
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183 | Wait till the result filehandle becomes ready for reading (simply |
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184 | does a select on the filehandle. This is useful if you want to |
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185 | synchronously wait for some requests to finish). |
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186 | |
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187 | See "nreqs" for an example. |
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188 | |
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189 | IO::AIO::nreqs |
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190 | Returns the number of requests currently outstanding. |
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191 | |
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192 | Example: wait till there are no outstanding requests anymore: |
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193 | |
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194 | IO::AIO::poll_wait, IO::AIO::poll_cb |
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195 | while IO::AIO::nreqs; |
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196 | |
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197 | IO::AIO::flush |
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198 | Wait till all outstanding AIO requests have been handled. |
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199 | |
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200 | Strictly equivalent to: |
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201 | |
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202 | IO::AIO::poll_wait, IO::AIO::poll_cb |
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203 | while IO::AIO::nreqs; |
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204 | |
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205 | IO::AIO::poll |
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206 | Waits until some requests have been handled. |
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207 | |
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208 | Strictly equivalent to: |
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209 | |
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210 | IO::AIO::poll_wait, IO::AIO::poll_cb |
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211 | if IO::AIO::nreqs; |
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212 | |
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213 | IO::AIO::min_parallel $nthreads |
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214 | Set the minimum number of AIO threads to $nthreads. The default is |
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215 | 1, which means a single asynchronous operation can be done at one |
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216 | time (the number of outstanding operations, however, is unlimited). |
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217 | |
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218 | It is recommended to keep the number of threads low, as some Linux |
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219 | kernel versions will scale negatively with the number of threads |
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220 | (higher parallelity => MUCH higher latency). With current Linux 2.6 |
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221 | versions, 4-32 threads should be fine. |
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222 | |
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223 | Under normal circumstances you don't need to call this function, as |
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224 | this module automatically starts some threads (the exact number |
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225 | might change, and is currently 4). |
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226 | |
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227 | IO::AIO::max_parallel $nthreads |
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228 | Sets the maximum number of AIO threads to $nthreads. If more than |
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229 | the specified number of threads are currently running, kill them. |
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230 | This function blocks until the limit is reached. |
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231 | |
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232 | This module automatically runs "max_parallel 0" at program end, to |
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233 | ensure that all threads are killed and that there are no outstanding |
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234 | requests. |
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235 | |
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236 | Under normal circumstances you don't need to call this function. |
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237 | |
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238 | $oldnreqs = IO::AIO::max_outstanding $nreqs |
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239 | Sets the maximum number of outstanding requests to $nreqs. If you |
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240 | try to queue up more than this number of requests, the caller will |
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241 | block until some requests have been handled. |
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242 | |
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243 | The default is very large, so normally there is no practical limit. |
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244 | If you queue up many requests in a loop it it often improves speed |
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245 | if you set this to a relatively low number, such as 100. |
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246 | |
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247 | Under normal circumstances you don't need to call this function. |
204 | |
248 | |
205 | SEE ALSO |
249 | SEE ALSO |
206 | Coro, Linux::AIO. |
250 | Coro, Linux::AIO. |
207 | |
251 | |
208 | AUTHOR |
252 | AUTHOR |