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 = shift |
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9 | or die "/etc/passwd: $!"; |
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10 | ... |
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11 | }; |
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12 | |
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13 | aio_unlink "/tmp/file", sub { }; |
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14 | |
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15 | aio_read $fh, 30000, 1024, $buffer, 0, sub { |
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16 | $_[0] > 0 or die "read error: $!"; |
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17 | }; |
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18 | |
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19 | # version 2+ has request and group objects |
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20 | use IO::AIO 2; |
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21 | |
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22 | aioreq_pri 4; # give next request a very high priority |
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23 | my $req = aio_unlink "/tmp/file", sub { }; |
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24 | $req->cancel; # cancel request if still in queue |
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25 | |
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26 | my $grp = aio_group sub { print "all stats done\n" }; |
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27 | add $grp aio_stat "..." for ...; |
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28 | |
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29 | # AnyEvent integration |
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30 | open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; |
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31 | my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb }); |
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32 | |
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33 | # Event integration |
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34 | Event->io (fd => IO::AIO::poll_fileno, |
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35 | poll => 'r', |
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36 | cb => \&IO::AIO::poll_cb); |
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37 | |
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38 | # Glib/Gtk2 integration |
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39 | add_watch Glib::IO IO::AIO::poll_fileno, |
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40 | in => sub { IO::AIO::poll_cb; 1 }; |
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41 | |
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42 | # Tk integration |
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43 | Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", |
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44 | readable => \&IO::AIO::poll_cb); |
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45 | |
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46 | # Danga::Socket integration |
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47 | Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => |
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48 | \&IO::AIO::poll_cb); |
6 | |
49 | |
7 | DESCRIPTION |
50 | DESCRIPTION |
8 | This module implements asynchronous I/O using whatever means your |
51 | This module implements asynchronous I/O using whatever means your |
9 | operating system supports. |
52 | operating system supports. |
10 | |
53 | |
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54 | Asynchronous means that operations that can normally block your program |
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55 | (e.g. reading from disk) will be done asynchronously: the operation will |
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56 | still block, but you can do something else in the meantime. This is |
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57 | extremely useful for programs that need to stay interactive even when |
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58 | doing heavy I/O (GUI programs, high performance network servers etc.), |
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59 | but can also be used to easily do operations in parallel that are |
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60 | normally done sequentially, e.g. stat'ing many files, which is much |
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61 | faster on a RAID volume or over NFS when you do a number of stat |
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62 | operations concurrently. |
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63 | |
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64 | While most of this works on all types of file descriptors (for example |
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65 | sockets), using these functions on file descriptors that support |
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66 | nonblocking operation (again, sockets, pipes etc.) is very inefficient |
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67 | or might not work (aio_read fails on sockets/pipes/fifos). Use an event |
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68 | loop for that (such as the Event module): IO::AIO will naturally fit |
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69 | into such an event loop itself. |
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70 | |
11 | Currently, a number of threads are started that execute your read/writes |
71 | In this version, a number of threads are started that execute your |
12 | and signal their completion. You don't need thread support in your libc |
72 | requests and signal their completion. You don't need thread support in |
13 | or perl, and the threads created by this module will not be visible to |
73 | perl, and the threads created by this module will not be visible to |
14 | the pthreads library. In the future, this module might make use of the |
74 | perl. In the future, this module might make use of the native aio |
15 | native aio functions available on many operating systems. However, they |
75 | functions available on many operating systems. However, they are often |
16 | are often not well-supported (Linux doesn't allow them on normal files |
76 | not well-supported or restricted (GNU/Linux doesn't allow them on normal |
17 | currently, for example), and they would only support aio_read and |
77 | files currently, for example), and they would only support aio_read and |
18 | aio_write, so the remaining functionality would have to be implemented |
78 | aio_write, so the remaining functionality would have to be implemented |
19 | using threads anyway. |
79 | using threads anyway. |
20 | |
80 | |
21 | Although the module will work with in the presence of other threads, it |
81 | Although the module will work with in the presence of other (Perl-) |
22 | is currently not reentrant, so use appropriate locking yourself. |
82 | threads, it is currently not reentrant in any way, so use appropriate |
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83 | locking yourself, always call "poll_cb" from within the same thread, or |
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84 | never call "poll_cb" (or other "aio_" functions) recursively. |
23 | |
85 | |
24 | API NOTES |
86 | EXAMPLE |
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87 | This is a simple example that uses the Event module and loads |
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88 | /etc/passwd asynchronously: |
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89 | |
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90 | use Fcntl; |
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91 | use Event; |
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92 | use IO::AIO; |
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93 | |
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94 | # register the IO::AIO callback with Event |
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95 | Event->io (fd => IO::AIO::poll_fileno, |
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96 | poll => 'r', |
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97 | cb => \&IO::AIO::poll_cb); |
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98 | |
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99 | # queue the request to open /etc/passwd |
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100 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
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101 | my $fh = shift |
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102 | or die "error while opening: $!"; |
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103 | |
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104 | # stat'ing filehandles is generally non-blocking |
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105 | my $size = -s $fh; |
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106 | |
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107 | # queue a request to read the file |
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108 | my $contents; |
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109 | aio_read $fh, 0, $size, $contents, 0, sub { |
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110 | $_[0] == $size |
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111 | or die "short read: $!"; |
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112 | |
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113 | close $fh; |
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114 | |
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115 | # file contents now in $contents |
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116 | print $contents; |
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117 | |
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118 | # exit event loop and program |
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119 | Event::unloop; |
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120 | }; |
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121 | }; |
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122 | |
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123 | # possibly queue up other requests, or open GUI windows, |
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124 | # check for sockets etc. etc. |
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125 | |
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126 | # process events as long as there are some: |
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127 | Event::loop; |
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128 | |
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129 | REQUEST ANATOMY AND LIFETIME |
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130 | Every "aio_*" function creates a request. which is a C data structure |
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131 | not directly visible to Perl. |
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132 | |
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133 | If called in non-void context, every request function returns a Perl |
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134 | object representing the request. In void context, nothing is returned, |
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135 | which saves a bit of memory. |
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136 | |
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137 | The perl object is a fairly standard ref-to-hash object. The hash |
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138 | contents are not used by IO::AIO so you are free to store anything you |
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139 | like in it. |
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140 | |
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141 | During their existance, aio requests travel through the following |
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142 | states, in order: |
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143 | |
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144 | ready |
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145 | Immediately after a request is created it is put into the ready |
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146 | state, waiting for a thread to execute it. |
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147 | |
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148 | execute |
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149 | A thread has accepted the request for processing and is currently |
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150 | executing it (e.g. blocking in read). |
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151 | |
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152 | pending |
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153 | The request has been executed and is waiting for result processing. |
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154 | |
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155 | While request submission and execution is fully asynchronous, result |
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156 | processing is not and relies on the perl interpreter calling |
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157 | "poll_cb" (or another function with the same effect). |
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158 | |
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159 | result |
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160 | The request results are processed synchronously by "poll_cb". |
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161 | |
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162 | The "poll_cb" function will process all outstanding aio requests by |
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163 | calling their callbacks, freeing memory associated with them and |
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164 | managing any groups they are contained in. |
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165 | |
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166 | done |
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167 | Request has reached the end of its lifetime and holds no resources |
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168 | anymore (except possibly for the Perl object, but its connection to |
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169 | the actual aio request is severed and calling its methods will |
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170 | either do nothing or result in a runtime error). |
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171 | |
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172 | FUNCTIONS |
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173 | AIO REQUEST FUNCTIONS |
25 | All the "aio_*" calls are more or less thin wrappers around the syscall |
174 | 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 |
175 | with the same name (sans "aio_"). The arguments are similar or |
27 | identical, and they all accept an additional $callback argument which |
176 | identical, and they all accept an additional (and optional) $callback |
28 | must be a code reference. This code reference will get called with the |
177 | 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, |
178 | 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 |
179 | error, unlike perl, which usually delivers "false") as it's sole |
31 | syscall has been executed asynchronously. |
180 | argument when the given syscall has been executed asynchronously. |
32 | |
181 | |
33 | All functions that expect a filehandle will also accept a file |
182 | All functions expecting a filehandle keep a copy of the filehandle |
34 | descriptor. |
183 | internally until the request has finished. |
35 | |
184 | |
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185 | All functions return request objects of type IO::AIO::REQ that allow |
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186 | further manipulation of those requests while they are in-flight. |
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187 | |
36 | The filenames you pass to these routines *must* be absolute. The reason |
188 | The pathnames you pass to these routines *must* be absolute and encoded |
37 | is that at the time the request is being executed, the current working |
189 | as octets. The reason for the former is that at the time the request is |
38 | directory could have changed. Alternatively, you can make sure that you |
190 | being executed, the current working directory could have changed. |
39 | never change the current working directory. |
191 | Alternatively, you can make sure that you never change the current |
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192 | working directory anywhere in the program and then use relative paths. |
40 | |
193 | |
41 | IO::AIO::min_parallel $nthreads |
194 | To encode pathnames as octets, either make sure you either: a) always |
42 | Set the minimum number of AIO threads to $nthreads. The default is |
195 | pass in filenames you got from outside (command line, readdir etc.) |
43 | 1, which means a single asynchronous operation can be done at one |
196 | without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module |
44 | time (the number of outstanding operations, however, is unlimited). |
197 | and encode your pathnames to the locale (or other) encoding in effect in |
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198 | the user environment, d) use Glib::filename_from_unicode on unicode |
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199 | filenames or e) use something else to ensure your scalar has the correct |
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200 | contents. |
45 | |
201 | |
46 | It is recommended to keep the number of threads low, as some linux |
202 | This works, btw. independent of the internal UTF-8 bit, which IO::AIO |
47 | kernel versions will scale negatively with the number of threads |
203 | handles correctly wether it is set or not. |
48 | (higher parallelity => MUCH higher latency). |
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49 | |
204 | |
50 | Under normal circumstances you don't need to call this function, as |
205 | $prev_pri = aioreq_pri [$pri] |
51 | this module automatically starts a single async thread. |
206 | Returns the priority value that would be used for the next request |
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207 | and, if $pri is given, sets the priority for the next aio request. |
52 | |
208 | |
53 | IO::AIO::max_parallel $nthreads |
209 | The default priority is 0, the minimum and maximum priorities are -4 |
54 | Sets the maximum number of AIO threads to $nthreads. If more than |
210 | and 4, respectively. Requests with higher priority will be serviced |
55 | the specified number of threads are currently running, kill them. |
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56 | This function blocks until the limit is reached. |
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57 | |
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58 | This module automatically runs "max_parallel 0" at program end, to |
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59 | ensure that all threads are killed and that there are no outstanding |
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60 | requests. |
211 | first. |
61 | |
212 | |
62 | Under normal circumstances you don't need to call this function. |
213 | The priority will be reset to 0 after each call to one of the |
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214 | "aio_*" functions. |
63 | |
215 | |
64 | $fileno = IO::AIO::poll_fileno |
216 | Example: open a file with low priority, then read something from it |
65 | Return the *request result pipe filehandle*. This filehandle must be |
217 | with higher priority so the read request is serviced before other |
66 | polled for reading by some mechanism outside this module (e.g. Event |
218 | low priority open requests (potentially spamming the cache): |
67 | or select, see below). If the pipe becomes readable you have to call |
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68 | "poll_cb" to check the results. |
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69 | |
219 | |
70 | See "poll_cb" for an example. |
220 | aioreq_pri -3; |
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221 | aio_open ..., sub { |
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222 | return unless $_[0]; |
71 | |
223 | |
72 | IO::AIO::poll_cb |
224 | aioreq_pri -2; |
73 | Process all outstanding events on the result pipe. You have to call |
225 | aio_read $_[0], ..., sub { |
74 | this regularly. Returns the number of events processed. Returns |
226 | ... |
75 | immediately when no events are outstanding. |
227 | }; |
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228 | }; |
76 | |
229 | |
77 | You can use Event to multiplex, e.g.: |
230 | aioreq_nice $pri_adjust |
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231 | Similar to "aioreq_pri", but subtracts the given value from the |
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232 | current priority, so the effect is cumulative. |
78 | |
233 | |
79 | Event->io (fd => IO::AIO::poll_fileno, |
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80 | poll => 'r', async => 1, |
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81 | cb => \&IO::AIO::poll_cb); |
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82 | |
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83 | IO::AIO::poll_wait |
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84 | Wait till the result filehandle becomes ready for reading (simply |
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85 | does a select on the filehandle. This is useful if you want to |
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86 | synchronously wait for some requests to finish). |
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87 | |
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88 | See "nreqs" for an example. |
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89 | |
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90 | IO::AIO::nreqs |
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91 | Returns the number of requests currently outstanding. |
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92 | |
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93 | Example: wait till there are no outstanding requests anymore: |
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94 | |
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95 | IO::AIO::poll_wait, IO::AIO::poll_cb |
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96 | while IO::AIO::nreqs; |
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97 | |
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98 | aio_open $pathname, $flags, $mode, $callback |
234 | aio_open $pathname, $flags, $mode, $callback->($fh) |
99 | Asynchronously open or create a file and call the callback with a |
235 | Asynchronously open or create a file and call the callback with a |
100 | newly created filehandle for the file. |
236 | newly created filehandle for the file. |
101 | |
237 | |
102 | The pathname passed to "aio_open" must be absolute. See API NOTES, |
238 | The pathname passed to "aio_open" must be absolute. See API NOTES, |
103 | above, for an explanation. |
239 | above, for an explanation. |
104 | |
240 | |
105 | The $mode argument is a bitmask. See the "Fcntl" module for a list. |
241 | The $flags argument is a bitmask. See the "Fcntl" module for a list. |
106 | They are the same as used in "sysopen". |
242 | They are the same as used by "sysopen". |
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243 | |
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244 | Likewise, $mode specifies the mode of the newly created file, if it |
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245 | didn't exist and "O_CREAT" has been given, just like perl's |
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246 | "sysopen", except that it is mandatory (i.e. use 0 if you don't |
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247 | create new files, and 0666 or 0777 if you do). |
107 | |
248 | |
108 | Example: |
249 | Example: |
109 | |
250 | |
110 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
251 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
111 | if ($_[0]) { |
252 | if ($_[0]) { |
… | |
… | |
114 | } else { |
255 | } else { |
115 | die "open failed: $!\n"; |
256 | die "open failed: $!\n"; |
116 | } |
257 | } |
117 | }; |
258 | }; |
118 | |
259 | |
119 | aio_close $fh, $callback |
260 | aio_close $fh, $callback->($status) |
120 | Asynchronously close a file and call the callback with the result |
261 | Asynchronously close a file and call the callback with the result |
121 | code. *WARNING:* although accepted, you should not pass in a perl |
262 | code. *WARNING:* although accepted, you should not pass in a perl |
122 | filehandle here, as perl will likely close the file descriptor |
263 | filehandle here, as perl will likely close the file descriptor |
123 | itself when the filehandle is destroyed. Normally, you can safely |
264 | another time when the filehandle is destroyed. Normally, you can |
124 | call perls "close" or just let filehandles go out of scope. |
265 | safely call perls "close" or just let filehandles go out of scope. |
125 | |
266 | |
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267 | This is supposed to be a bug in the API, so that might change. It's |
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268 | therefore best to avoid this function. |
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269 | |
126 | aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
270 | aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
127 | aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
271 | aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
128 | Reads or writes "length" bytes from the specified "fh" and "offset" |
272 | Reads or writes "length" bytes from the specified "fh" and "offset" |
129 | into the scalar given by "data" and offset "dataoffset" and calls |
273 | into the scalar given by "data" and offset "dataoffset" and calls |
130 | the callback without the actual number of bytes read (or -1 on |
274 | the callback without the actual number of bytes read (or -1 on |
131 | error, just like the syscall). |
275 | error, just like the syscall). |
132 | |
276 | |
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277 | The $data scalar *MUST NOT* be modified in any way while the request |
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278 | is outstanding. Modifying it can result in segfaults or WW3 (if the |
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279 | necessary/optional hardware is installed). |
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280 | |
133 | Example: Read 15 bytes at offset 7 into scalar $buffer, strating at |
281 | Example: Read 15 bytes at offset 7 into scalar $buffer, starting at |
134 | offset 0 within the scalar: |
282 | offset 0 within the scalar: |
135 | |
283 | |
136 | aio_read $fh, 7, 15, $buffer, 0, sub { |
284 | aio_read $fh, 7, 15, $buffer, 0, sub { |
137 | $_[0] >= 0 or die "read error: $!"; |
285 | $_[0] > 0 or die "read error: $!"; |
138 | print "read <$buffer>\n"; |
286 | print "read $_[0] bytes: <$buffer>\n"; |
139 | }; |
287 | }; |
140 | |
288 | |
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289 | aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) |
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290 | Tries to copy $length bytes from $in_fh to $out_fh. It starts |
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291 | reading at byte offset $in_offset, and starts writing at the current |
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292 | file offset of $out_fh. Because of that, it is not safe to issue |
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293 | more than one "aio_sendfile" per $out_fh, as they will interfere |
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294 | with each other. |
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295 | |
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296 | This call tries to make use of a native "sendfile" syscall to |
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297 | provide zero-copy operation. For this to work, $out_fh should refer |
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298 | to a socket, and $in_fh should refer to mmap'able file. |
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299 | |
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300 | If the native sendfile call fails or is not implemented, it will be |
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301 | emulated, so you can call "aio_sendfile" on any type of filehandle |
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302 | regardless of the limitations of the operating system. |
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303 | |
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304 | Please note, however, that "aio_sendfile" can read more bytes from |
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305 | $in_fh than are written, and there is no way to find out how many |
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306 | bytes have been read from "aio_sendfile" alone, as "aio_sendfile" |
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307 | only provides the number of bytes written to $out_fh. Only if the |
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308 | result value equals $length one can assume that $length bytes have |
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309 | been read. |
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310 | |
141 | aio_readahead $fh,$offset,$length, $callback |
311 | aio_readahead $fh,$offset,$length, $callback->($retval) |
142 | Asynchronously reads the specified byte range into the page cache, |
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143 | using the "readahead" syscall. If that syscall doesn't exist the |
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144 | status will be -1 and $! is set to ENOSYS. |
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145 | |
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146 | readahead() populates the page cache with data from a file so that |
312 | "aio_readahead" populates the page cache with data from a file so |
147 | subsequent reads from that file will not block on disk I/O. The |
313 | that subsequent reads from that file will not block on disk I/O. The |
148 | $offset argument specifies the starting point from which data is to |
314 | $offset argument specifies the starting point from which data is to |
149 | be read and $length specifies the number of bytes to be read. I/O is |
315 | be read and $length specifies the number of bytes to be read. I/O is |
150 | performed in whole pages, so that offset is effectively rounded down |
316 | performed in whole pages, so that offset is effectively rounded down |
151 | to a page boundary and bytes are read up to the next page boundary |
317 | to a page boundary and bytes are read up to the next page boundary |
152 | greater than or equal to (off-set+length). aio_readahead() does not |
318 | greater than or equal to (off-set+length). "aio_readahead" does not |
153 | read beyond the end of the file. The current file offset of the file |
319 | read beyond the end of the file. The current file offset of the file |
154 | is left unchanged. |
320 | is left unchanged. |
155 | |
321 | |
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322 | If that syscall doesn't exist (likely if your OS isn't Linux) it |
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323 | will be emulated by simply reading the data, which would have a |
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324 | similar effect. |
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325 | |
156 | aio_stat $fh_or_path, $callback |
326 | aio_stat $fh_or_path, $callback->($status) |
157 | aio_lstat $fh, $callback |
327 | aio_lstat $fh, $callback->($status) |
158 | Works like perl's "stat" or "lstat" in void context. The callback |
328 | Works like perl's "stat" or "lstat" in void context. The callback |
159 | will be called after the stat and the results will be available |
329 | will be called after the stat and the results will be available |
160 | using "stat _" or "-s _" etc... |
330 | using "stat _" or "-s _" etc... |
161 | |
331 | |
162 | The pathname passed to "aio_stat" must be absolute. See API NOTES, |
332 | The pathname passed to "aio_stat" must be absolute. See API NOTES, |
… | |
… | |
172 | aio_stat "/etc/passwd", sub { |
342 | aio_stat "/etc/passwd", sub { |
173 | $_[0] and die "stat failed: $!"; |
343 | $_[0] and die "stat failed: $!"; |
174 | print "size is ", -s _, "\n"; |
344 | print "size is ", -s _, "\n"; |
175 | }; |
345 | }; |
176 | |
346 | |
177 | aio_unlink $pathname, $callback |
347 | aio_unlink $pathname, $callback->($status) |
178 | Asynchronously unlink (delete) a file and call the callback with the |
348 | Asynchronously unlink (delete) a file and call the callback with the |
179 | result code. |
349 | result code. |
180 | |
350 | |
|
|
351 | aio_mknod $path, $mode, $dev, $callback->($status) |
|
|
352 | [EXPERIMENTAL] |
|
|
353 | |
|
|
354 | Asynchronously create a device node (or fifo). See mknod(2). |
|
|
355 | |
|
|
356 | The only (POSIX-) portable way of calling this function is: |
|
|
357 | |
|
|
358 | aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... |
|
|
359 | |
|
|
360 | aio_link $srcpath, $dstpath, $callback->($status) |
|
|
361 | Asynchronously create a new link to the existing object at $srcpath |
|
|
362 | at the path $dstpath and call the callback with the result code. |
|
|
363 | |
|
|
364 | aio_symlink $srcpath, $dstpath, $callback->($status) |
|
|
365 | Asynchronously create a new symbolic link to the existing object at |
|
|
366 | $srcpath at the path $dstpath and call the callback with the result |
|
|
367 | code. |
|
|
368 | |
|
|
369 | aio_readlink $path, $callback->($link) |
|
|
370 | Asynchronously read the symlink specified by $path and pass it to |
|
|
371 | the callback. If an error occurs, nothing or undef gets passed to |
|
|
372 | the callback. |
|
|
373 | |
|
|
374 | aio_rename $srcpath, $dstpath, $callback->($status) |
|
|
375 | Asynchronously rename the object at $srcpath to $dstpath, just as |
|
|
376 | rename(2) and call the callback with the result code. |
|
|
377 | |
|
|
378 | aio_rmdir $pathname, $callback->($status) |
|
|
379 | Asynchronously rmdir (delete) a directory and call the callback with |
|
|
380 | the result code. |
|
|
381 | |
|
|
382 | aio_readdir $pathname, $callback->($entries) |
|
|
383 | Unlike the POSIX call of the same name, "aio_readdir" reads an |
|
|
384 | entire directory (i.e. opendir + readdir + closedir). The entries |
|
|
385 | will not be sorted, and will NOT include the "." and ".." entries. |
|
|
386 | |
|
|
387 | The callback a single argument which is either "undef" or an |
|
|
388 | array-ref with the filenames. |
|
|
389 | |
|
|
390 | aio_load $path, $data, $callback->($status) |
|
|
391 | This is a composite request that tries to fully load the given file |
|
|
392 | into memory. Status is the same as with aio_read. |
|
|
393 | |
|
|
394 | aio_copy $srcpath, $dstpath, $callback->($status) |
|
|
395 | Try to copy the *file* (directories not supported as either source |
|
|
396 | or destination) from $srcpath to $dstpath and call the callback with |
|
|
397 | the 0 (error) or -1 ok. |
|
|
398 | |
|
|
399 | This is a composite request that it creates the destination file |
|
|
400 | with mode 0200 and copies the contents of the source file into it |
|
|
401 | using "aio_sendfile", followed by restoring atime, mtime, access |
|
|
402 | mode and uid/gid, in that order. |
|
|
403 | |
|
|
404 | If an error occurs, the partial destination file will be unlinked, |
|
|
405 | if possible, except when setting atime, mtime, access mode and |
|
|
406 | uid/gid, where errors are being ignored. |
|
|
407 | |
|
|
408 | aio_move $srcpath, $dstpath, $callback->($status) |
|
|
409 | Try to move the *file* (directories not supported as either source |
|
|
410 | or destination) from $srcpath to $dstpath and call the callback with |
|
|
411 | the 0 (error) or -1 ok. |
|
|
412 | |
|
|
413 | This is a composite request that tries to rename(2) the file first. |
|
|
414 | If rename files with "EXDEV", it copies the file with "aio_copy" |
|
|
415 | and, if that is successful, unlinking the $srcpath. |
|
|
416 | |
|
|
417 | aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) |
|
|
418 | Scans a directory (similar to "aio_readdir") but additionally tries |
|
|
419 | to efficiently separate the entries of directory $path into two sets |
|
|
420 | of names, directories you can recurse into (directories), and ones |
|
|
421 | you cannot recurse into (everything else, including symlinks to |
|
|
422 | directories). |
|
|
423 | |
|
|
424 | "aio_scandir" is a composite request that creates of many sub |
|
|
425 | requests_ $maxreq specifies the maximum number of outstanding aio |
|
|
426 | requests that this function generates. If it is "<= 0", then a |
|
|
427 | suitable default will be chosen (currently 4). |
|
|
428 | |
|
|
429 | On error, the callback is called without arguments, otherwise it |
|
|
430 | receives two array-refs with path-relative entry names. |
|
|
431 | |
|
|
432 | Example: |
|
|
433 | |
|
|
434 | aio_scandir $dir, 0, sub { |
|
|
435 | my ($dirs, $nondirs) = @_; |
|
|
436 | print "real directories: @$dirs\n"; |
|
|
437 | print "everything else: @$nondirs\n"; |
|
|
438 | }; |
|
|
439 | |
|
|
440 | Implementation notes. |
|
|
441 | |
|
|
442 | The "aio_readdir" cannot be avoided, but "stat()"'ing every entry |
|
|
443 | can. |
|
|
444 | |
|
|
445 | After reading the directory, the modification time, size etc. of the |
|
|
446 | directory before and after the readdir is checked, and if they match |
|
|
447 | (and isn't the current time), the link count will be used to decide |
|
|
448 | how many entries are directories (if >= 2). Otherwise, no knowledge |
|
|
449 | of the number of subdirectories will be assumed. |
|
|
450 | |
|
|
451 | Then entries will be sorted into likely directories (everything |
|
|
452 | without a non-initial dot currently) and likely non-directories |
|
|
453 | (everything else). Then every entry plus an appended "/." will be |
|
|
454 | "stat"'ed, likely directories first. If that succeeds, it assumes |
|
|
455 | that the entry is a directory or a symlink to directory (which will |
|
|
456 | be checked seperately). This is often faster than stat'ing the entry |
|
|
457 | itself because filesystems might detect the type of the entry |
|
|
458 | without reading the inode data (e.g. ext2fs filetype feature). |
|
|
459 | |
|
|
460 | If the known number of directories (link count - 2) has been |
|
|
461 | reached, the rest of the entries is assumed to be non-directories. |
|
|
462 | |
|
|
463 | This only works with certainty on POSIX (= UNIX) filesystems, which |
|
|
464 | fortunately are the vast majority of filesystems around. |
|
|
465 | |
|
|
466 | It will also likely work on non-POSIX filesystems with reduced |
|
|
467 | efficiency as those tend to return 0 or 1 as link counts, which |
|
|
468 | disables the directory counting heuristic. |
|
|
469 | |
181 | aio_fsync $fh, $callback |
470 | aio_fsync $fh, $callback->($status) |
182 | Asynchronously call fsync on the given filehandle and call the |
471 | Asynchronously call fsync on the given filehandle and call the |
183 | callback with the fsync result code. |
472 | callback with the fsync result code. |
184 | |
473 | |
185 | aio_fdatasync $fh, $callback |
474 | aio_fdatasync $fh, $callback->($status) |
186 | Asynchronously call fdatasync on the given filehandle and call the |
475 | Asynchronously call fdatasync on the given filehandle and call the |
187 | callback with the fdatasync result code. |
476 | callback with the fdatasync result code. |
188 | |
477 | |
189 | BUGS |
478 | If this call isn't available because your OS lacks it or it couldn't |
190 | - could be optimized to use more semaphores instead of filehandles. |
479 | be detected, it will be emulated by calling "fsync" instead. |
|
|
480 | |
|
|
481 | aio_group $callback->(...) |
|
|
482 | This is a very special aio request: Instead of doing something, it |
|
|
483 | is a container for other aio requests, which is useful if you want |
|
|
484 | to bundle many requests into a single, composite, request with a |
|
|
485 | definite callback and the ability to cancel the whole request with |
|
|
486 | its subrequests. |
|
|
487 | |
|
|
488 | Returns an object of class IO::AIO::GRP. See its documentation below |
|
|
489 | for more info. |
|
|
490 | |
|
|
491 | Example: |
|
|
492 | |
|
|
493 | my $grp = aio_group sub { |
|
|
494 | print "all stats done\n"; |
|
|
495 | }; |
|
|
496 | |
|
|
497 | add $grp |
|
|
498 | (aio_stat ...), |
|
|
499 | (aio_stat ...), |
|
|
500 | ...; |
|
|
501 | |
|
|
502 | aio_nop $callback->() |
|
|
503 | This is a special request - it does nothing in itself and is only |
|
|
504 | used for side effects, such as when you want to add a dummy request |
|
|
505 | to a group so that finishing the requests in the group depends on |
|
|
506 | executing the given code. |
|
|
507 | |
|
|
508 | While this request does nothing, it still goes through the execution |
|
|
509 | phase and still requires a worker thread. Thus, the callback will |
|
|
510 | not be executed immediately but only after other requests in the |
|
|
511 | queue have entered their execution phase. This can be used to |
|
|
512 | measure request latency. |
|
|
513 | |
|
|
514 | IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED* |
|
|
515 | Mainly used for debugging and benchmarking, this aio request puts |
|
|
516 | one of the request workers to sleep for the given time. |
|
|
517 | |
|
|
518 | While it is theoretically handy to have simple I/O scheduling |
|
|
519 | requests like sleep and file handle readable/writable, the overhead |
|
|
520 | this creates is immense (it blocks a thread for a long time) so do |
|
|
521 | not use this function except to put your application under |
|
|
522 | artificial I/O pressure. |
|
|
523 | |
|
|
524 | IO::AIO::REQ CLASS |
|
|
525 | All non-aggregate "aio_*" functions return an object of this class when |
|
|
526 | called in non-void context. |
|
|
527 | |
|
|
528 | cancel $req |
|
|
529 | Cancels the request, if possible. Has the effect of skipping |
|
|
530 | execution when entering the execute state and skipping calling the |
|
|
531 | callback when entering the the result state, but will leave the |
|
|
532 | request otherwise untouched. That means that requests that currently |
|
|
533 | execute will not be stopped and resources held by the request will |
|
|
534 | not be freed prematurely. |
|
|
535 | |
|
|
536 | cb $req $callback->(...) |
|
|
537 | Replace (or simply set) the callback registered to the request. |
|
|
538 | |
|
|
539 | IO::AIO::GRP CLASS |
|
|
540 | This class is a subclass of IO::AIO::REQ, so all its methods apply to |
|
|
541 | objects of this class, too. |
|
|
542 | |
|
|
543 | A IO::AIO::GRP object is a special request that can contain multiple |
|
|
544 | other aio requests. |
|
|
545 | |
|
|
546 | You create one by calling the "aio_group" constructing function with a |
|
|
547 | callback that will be called when all contained requests have entered |
|
|
548 | the "done" state: |
|
|
549 | |
|
|
550 | my $grp = aio_group sub { |
|
|
551 | print "all requests are done\n"; |
|
|
552 | }; |
|
|
553 | |
|
|
554 | You add requests by calling the "add" method with one or more |
|
|
555 | "IO::AIO::REQ" objects: |
|
|
556 | |
|
|
557 | $grp->add (aio_unlink "..."); |
|
|
558 | |
|
|
559 | add $grp aio_stat "...", sub { |
|
|
560 | $_[0] or return $grp->result ("error"); |
|
|
561 | |
|
|
562 | # add another request dynamically, if first succeeded |
|
|
563 | add $grp aio_open "...", sub { |
|
|
564 | $grp->result ("ok"); |
|
|
565 | }; |
|
|
566 | }; |
|
|
567 | |
|
|
568 | This makes it very easy to create composite requests (see the source of |
|
|
569 | "aio_move" for an application) that work and feel like simple requests. |
|
|
570 | |
|
|
571 | * The IO::AIO::GRP objects will be cleaned up during calls to |
|
|
572 | "IO::AIO::poll_cb", just like any other request. |
|
|
573 | * They can be canceled like any other request. Canceling will cancel not |
|
|
574 | only the request itself, but also all requests it contains. |
|
|
575 | * They can also can also be added to other IO::AIO::GRP objects. |
|
|
576 | * You must not add requests to a group from within the group callback |
|
|
577 | (or any later time). |
|
|
578 | |
|
|
579 | Their lifetime, simplified, looks like this: when they are empty, they |
|
|
580 | will finish very quickly. If they contain only requests that are in the |
|
|
581 | "done" state, they will also finish. Otherwise they will continue to |
|
|
582 | exist. |
|
|
583 | |
|
|
584 | That means after creating a group you have some time to add requests. |
|
|
585 | And in the callbacks of those requests, you can add further requests to |
|
|
586 | the group. And only when all those requests have finished will the the |
|
|
587 | group itself finish. |
|
|
588 | |
|
|
589 | add $grp ... |
|
|
590 | $grp->add (...) |
|
|
591 | Add one or more requests to the group. Any type of IO::AIO::REQ can |
|
|
592 | be added, including other groups, as long as you do not create |
|
|
593 | circular dependencies. |
|
|
594 | |
|
|
595 | Returns all its arguments. |
|
|
596 | |
|
|
597 | $grp->cancel_subs |
|
|
598 | Cancel all subrequests and clears any feeder, but not the group |
|
|
599 | request itself. Useful when you queued a lot of events but got a |
|
|
600 | result early. |
|
|
601 | |
|
|
602 | $grp->result (...) |
|
|
603 | Set the result value(s) that will be passed to the group callback |
|
|
604 | when all subrequests have finished and set thre groups errno to the |
|
|
605 | current value of errno (just like calling "errno" without an error |
|
|
606 | number). By default, no argument will be passed and errno is zero. |
|
|
607 | |
|
|
608 | $grp->errno ([$errno]) |
|
|
609 | Sets the group errno value to $errno, or the current value of errno |
|
|
610 | when the argument is missing. |
|
|
611 | |
|
|
612 | Every aio request has an associated errno value that is restored |
|
|
613 | when the callback is invoked. This method lets you change this value |
|
|
614 | from its default (0). |
|
|
615 | |
|
|
616 | Calling "result" will also set errno, so make sure you either set $! |
|
|
617 | before the call to "result", or call c<errno> after it. |
|
|
618 | |
|
|
619 | feed $grp $callback->($grp) |
|
|
620 | Sets a feeder/generator on this group: every group can have an |
|
|
621 | attached generator that generates requests if idle. The idea behind |
|
|
622 | this is that, although you could just queue as many requests as you |
|
|
623 | want in a group, this might starve other requests for a potentially |
|
|
624 | long time. For example, "aio_scandir" might generate hundreds of |
|
|
625 | thousands "aio_stat" requests, delaying any later requests for a |
|
|
626 | long time. |
|
|
627 | |
|
|
628 | To avoid this, and allow incremental generation of requests, you can |
|
|
629 | instead a group and set a feeder on it that generates those |
|
|
630 | requests. The feed callback will be called whenever there are few |
|
|
631 | enough (see "limit", below) requests active in the group itself and |
|
|
632 | is expected to queue more requests. |
|
|
633 | |
|
|
634 | The feed callback can queue as many requests as it likes (i.e. "add" |
|
|
635 | does not impose any limits). |
|
|
636 | |
|
|
637 | If the feed does not queue more requests when called, it will be |
|
|
638 | automatically removed from the group. |
|
|
639 | |
|
|
640 | If the feed limit is 0, it will be set to 2 automatically. |
|
|
641 | |
|
|
642 | Example: |
|
|
643 | |
|
|
644 | # stat all files in @files, but only ever use four aio requests concurrently: |
|
|
645 | |
|
|
646 | my $grp = aio_group sub { print "finished\n" }; |
|
|
647 | limit $grp 4; |
|
|
648 | feed $grp sub { |
|
|
649 | my $file = pop @files |
|
|
650 | or return; |
|
|
651 | |
|
|
652 | add $grp aio_stat $file, sub { ... }; |
|
|
653 | }; |
|
|
654 | |
|
|
655 | limit $grp $num |
|
|
656 | Sets the feeder limit for the group: The feeder will be called |
|
|
657 | whenever the group contains less than this many requests. |
|
|
658 | |
|
|
659 | Setting the limit to 0 will pause the feeding process. |
|
|
660 | |
|
|
661 | SUPPORT FUNCTIONS |
|
|
662 | EVENT PROCESSING AND EVENT LOOP INTEGRATION |
|
|
663 | $fileno = IO::AIO::poll_fileno |
|
|
664 | Return the *request result pipe file descriptor*. This filehandle |
|
|
665 | must be polled for reading by some mechanism outside this module |
|
|
666 | (e.g. Event or select, see below or the SYNOPSIS). If the pipe |
|
|
667 | becomes readable you have to call "poll_cb" to check the results. |
|
|
668 | |
|
|
669 | See "poll_cb" for an example. |
|
|
670 | |
|
|
671 | IO::AIO::poll_cb |
|
|
672 | Process some outstanding events on the result pipe. You have to call |
|
|
673 | this regularly. Returns the number of events processed. Returns |
|
|
674 | immediately when no events are outstanding. The amount of events |
|
|
675 | processed depends on the settings of "IO::AIO::max_poll_req" and |
|
|
676 | "IO::AIO::max_poll_time". |
|
|
677 | |
|
|
678 | If not all requests were processed for whatever reason, the |
|
|
679 | filehandle will still be ready when "poll_cb" returns. |
|
|
680 | |
|
|
681 | Example: Install an Event watcher that automatically calls |
|
|
682 | IO::AIO::poll_cb with high priority: |
|
|
683 | |
|
|
684 | Event->io (fd => IO::AIO::poll_fileno, |
|
|
685 | poll => 'r', async => 1, |
|
|
686 | cb => \&IO::AIO::poll_cb); |
|
|
687 | |
|
|
688 | IO::AIO::max_poll_reqs $nreqs |
|
|
689 | IO::AIO::max_poll_time $seconds |
|
|
690 | These set the maximum number of requests (default 0, meaning |
|
|
691 | infinity) that are being processed by "IO::AIO::poll_cb" in one |
|
|
692 | call, respectively the maximum amount of time (default 0, meaning |
|
|
693 | infinity) spent in "IO::AIO::poll_cb" to process requests (more |
|
|
694 | correctly the mininum amount of time "poll_cb" is allowed to use). |
|
|
695 | |
|
|
696 | Setting "max_poll_time" to a non-zero value creates an overhead of |
|
|
697 | one syscall per request processed, which is not normally a problem |
|
|
698 | unless your callbacks are really really fast or your OS is really |
|
|
699 | really slow (I am not mentioning Solaris here). Using |
|
|
700 | "max_poll_reqs" incurs no overhead. |
|
|
701 | |
|
|
702 | Setting these is useful if you want to ensure some level of |
|
|
703 | interactiveness when perl is not fast enough to process all requests |
|
|
704 | in time. |
|
|
705 | |
|
|
706 | For interactive programs, values such as 0.01 to 0.1 should be fine. |
|
|
707 | |
|
|
708 | Example: Install an Event watcher that automatically calls |
|
|
709 | IO::AIO::poll_cb with low priority, to ensure that other parts of |
|
|
710 | the program get the CPU sometimes even under high AIO load. |
|
|
711 | |
|
|
712 | # try not to spend much more than 0.1s in poll_cb |
|
|
713 | IO::AIO::max_poll_time 0.1; |
|
|
714 | |
|
|
715 | # use a low priority so other tasks have priority |
|
|
716 | Event->io (fd => IO::AIO::poll_fileno, |
|
|
717 | poll => 'r', nice => 1, |
|
|
718 | cb => &IO::AIO::poll_cb); |
|
|
719 | |
|
|
720 | IO::AIO::poll_wait |
|
|
721 | If there are any outstanding requests and none of them in the result |
|
|
722 | phase, wait till the result filehandle becomes ready for reading |
|
|
723 | (simply does a "select" on the filehandle. This is useful if you |
|
|
724 | want to synchronously wait for some requests to finish). |
|
|
725 | |
|
|
726 | See "nreqs" for an example. |
|
|
727 | |
|
|
728 | IO::AIO::poll |
|
|
729 | Waits until some requests have been handled. |
|
|
730 | |
|
|
731 | Returns the number of requests processed, but is otherwise strictly |
|
|
732 | equivalent to: |
|
|
733 | |
|
|
734 | IO::AIO::poll_wait, IO::AIO::poll_cb |
|
|
735 | |
|
|
736 | IO::AIO::flush |
|
|
737 | Wait till all outstanding AIO requests have been handled. |
|
|
738 | |
|
|
739 | Strictly equivalent to: |
|
|
740 | |
|
|
741 | IO::AIO::poll_wait, IO::AIO::poll_cb |
|
|
742 | while IO::AIO::nreqs; |
|
|
743 | |
|
|
744 | CONTROLLING THE NUMBER OF THREADS |
|
|
745 | IO::AIO::min_parallel $nthreads |
|
|
746 | Set the minimum number of AIO threads to $nthreads. The current |
|
|
747 | default is 8, which means eight asynchronous operations can execute |
|
|
748 | concurrently at any one time (the number of outstanding requests, |
|
|
749 | however, is unlimited). |
|
|
750 | |
|
|
751 | IO::AIO starts threads only on demand, when an AIO request is queued |
|
|
752 | and no free thread exists. Please note that queueing up a hundred |
|
|
753 | requests can create demand for a hundred threads, even if it turns |
|
|
754 | out that everything is in the cache and could have been processed |
|
|
755 | faster by a single thread. |
|
|
756 | |
|
|
757 | It is recommended to keep the number of threads relatively low, as |
|
|
758 | some Linux kernel versions will scale negatively with the number of |
|
|
759 | threads (higher parallelity => MUCH higher latency). With current |
|
|
760 | Linux 2.6 versions, 4-32 threads should be fine. |
|
|
761 | |
|
|
762 | Under most circumstances you don't need to call this function, as |
|
|
763 | the module selects a default that is suitable for low to moderate |
|
|
764 | load. |
|
|
765 | |
|
|
766 | IO::AIO::max_parallel $nthreads |
|
|
767 | Sets the maximum number of AIO threads to $nthreads. If more than |
|
|
768 | the specified number of threads are currently running, this function |
|
|
769 | kills them. This function blocks until the limit is reached. |
|
|
770 | |
|
|
771 | While $nthreads are zero, aio requests get queued but not executed |
|
|
772 | until the number of threads has been increased again. |
|
|
773 | |
|
|
774 | This module automatically runs "max_parallel 0" at program end, to |
|
|
775 | ensure that all threads are killed and that there are no outstanding |
|
|
776 | requests. |
|
|
777 | |
|
|
778 | Under normal circumstances you don't need to call this function. |
|
|
779 | |
|
|
780 | IO::AIO::max_idle $nthreads |
|
|
781 | Limit the number of threads (default: 4) that are allowed to idle |
|
|
782 | (i.e., threads that did not get a request to process within 10 |
|
|
783 | seconds). That means if a thread becomes idle while $nthreads other |
|
|
784 | threads are also idle, it will free its resources and exit. |
|
|
785 | |
|
|
786 | This is useful when you allow a large number of threads (e.g. 100 or |
|
|
787 | 1000) to allow for extremely high load situations, but want to free |
|
|
788 | resources under normal circumstances (1000 threads can easily |
|
|
789 | consume 30MB of RAM). |
|
|
790 | |
|
|
791 | The default is probably ok in most situations, especially if thread |
|
|
792 | creation is fast. If thread creation is very slow on your system you |
|
|
793 | might want to use larger values. |
|
|
794 | |
|
|
795 | $oldmaxreqs = IO::AIO::max_outstanding $maxreqs |
|
|
796 | This is a very bad function to use in interactive programs because |
|
|
797 | it blocks, and a bad way to reduce concurrency because it is |
|
|
798 | inexact: Better use an "aio_group" together with a feed callback. |
|
|
799 | |
|
|
800 | Sets the maximum number of outstanding requests to $nreqs. If you to |
|
|
801 | queue up more than this number of requests, the next call to the |
|
|
802 | "poll_cb" (and "poll_some" and other functions calling "poll_cb") |
|
|
803 | function will block until the limit is no longer exceeded. |
|
|
804 | |
|
|
805 | The default value is very large, so there is no practical limit on |
|
|
806 | the number of outstanding requests. |
|
|
807 | |
|
|
808 | You can still queue as many requests as you want. Therefore, |
|
|
809 | "max_oustsanding" is mainly useful in simple scripts (with low |
|
|
810 | values) or as a stop gap to shield against fatal memory overflow |
|
|
811 | (with large values). |
|
|
812 | |
|
|
813 | STATISTICAL INFORMATION |
|
|
814 | IO::AIO::nreqs |
|
|
815 | Returns the number of requests currently in the ready, execute or |
|
|
816 | pending states (i.e. for which their callback has not been invoked |
|
|
817 | yet). |
|
|
818 | |
|
|
819 | Example: wait till there are no outstanding requests anymore: |
|
|
820 | |
|
|
821 | IO::AIO::poll_wait, IO::AIO::poll_cb |
|
|
822 | while IO::AIO::nreqs; |
|
|
823 | |
|
|
824 | IO::AIO::nready |
|
|
825 | Returns the number of requests currently in the ready state (not yet |
|
|
826 | executed). |
|
|
827 | |
|
|
828 | IO::AIO::npending |
|
|
829 | Returns the number of requests currently in the pending state |
|
|
830 | (executed, but not yet processed by poll_cb). |
|
|
831 | |
|
|
832 | FORK BEHAVIOUR |
|
|
833 | This module should do "the right thing" when the process using it forks: |
|
|
834 | |
|
|
835 | Before the fork, IO::AIO enters a quiescent state where no requests can |
|
|
836 | be added in other threads and no results will be processed. After the |
|
|
837 | fork the parent simply leaves the quiescent state and continues |
|
|
838 | request/result processing, while the child frees the request/result |
|
|
839 | queue (so that the requests started before the fork will only be handled |
|
|
840 | in the parent). Threads will be started on demand until the limit set in |
|
|
841 | the parent process has been reached again. |
|
|
842 | |
|
|
843 | In short: the parent will, after a short pause, continue as if fork had |
|
|
844 | not been called, while the child will act as if IO::AIO has not been |
|
|
845 | used yet. |
|
|
846 | |
|
|
847 | MEMORY USAGE |
|
|
848 | Per-request usage: |
|
|
849 | |
|
|
850 | Each aio request uses - depending on your architecture - around 100-200 |
|
|
851 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
|
|
852 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
|
|
853 | scalars and other data passed into aio requests will also be locked and |
|
|
854 | will consume memory till the request has entered the done state. |
|
|
855 | |
|
|
856 | This is now awfully much, so queuing lots of requests is not usually a |
|
|
857 | problem. |
|
|
858 | |
|
|
859 | Per-thread usage: |
|
|
860 | |
|
|
861 | In the execution phase, some aio requests require more memory for |
|
|
862 | temporary buffers, and each thread requires a stack and other data |
|
|
863 | structures (usually around 16k-128k, depending on the OS). |
|
|
864 | |
|
|
865 | KNOWN BUGS |
|
|
866 | Known bugs will be fixed in the next release. |
191 | |
867 | |
192 | SEE ALSO |
868 | SEE ALSO |
193 | Coro, Linux::AIO. |
869 | Coro::AIO. |
194 | |
870 | |
195 | AUTHOR |
871 | AUTHOR |
196 | Marc Lehmann <schmorp@schmorp.de> |
872 | Marc Lehmann <schmorp@schmorp.de> |
197 | http://home.schmorp.de/ |
873 | http://home.schmorp.de/ |
198 | |
874 | |