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 (EV, Event, Glib, Tk, POE, urxvt, pureperl...) |
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30 | use AnyEvent::AIO; |
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31 | |
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32 | # EV integration |
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33 | my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb; |
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34 | |
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35 | # Event integration |
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36 | Event->io (fd => IO::AIO::poll_fileno, |
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37 | poll => 'r', |
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38 | cb => \&IO::AIO::poll_cb); |
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39 | |
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40 | # Glib/Gtk2 integration |
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41 | add_watch Glib::IO IO::AIO::poll_fileno, |
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42 | in => sub { IO::AIO::poll_cb; 1 }; |
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43 | |
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44 | # Tk integration |
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45 | Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", |
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46 | readable => \&IO::AIO::poll_cb); |
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47 | |
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48 | # Danga::Socket integration |
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49 | Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => |
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50 | \&IO::AIO::poll_cb); |
6 | |
51 | |
7 | DESCRIPTION |
52 | DESCRIPTION |
8 | This module implements asynchronous I/O using whatever means your |
53 | This module implements asynchronous I/O using whatever means your |
9 | operating system supports. |
54 | operating system supports. |
10 | |
55 | |
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56 | Asynchronous means that operations that can normally block your program |
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57 | (e.g. reading from disk) will be done asynchronously: the operation will |
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58 | still block, but you can do something else in the meantime. This is |
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59 | extremely useful for programs that need to stay interactive even when |
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60 | doing heavy I/O (GUI programs, high performance network servers etc.), |
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61 | but can also be used to easily do operations in parallel that are |
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62 | normally done sequentially, e.g. stat'ing many files, which is much |
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63 | faster on a RAID volume or over NFS when you do a number of stat |
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64 | operations concurrently. |
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65 | |
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66 | While most of this works on all types of file descriptors (for example |
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67 | sockets), using these functions on file descriptors that support |
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68 | nonblocking operation (again, sockets, pipes etc.) is very inefficient. |
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69 | Use an event loop for that (such as the Event module): IO::AIO will |
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70 | naturally fit into such an event loop itself. |
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71 | |
11 | Currently, a number of threads are started that execute your read/writes |
72 | 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 |
73 | 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 |
74 | 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 |
75 | perl. In the future, this module might make use of the native aio |
15 | native aio functions available on many operating systems. However, they |
76 | functions available on many operating systems. However, they are often |
16 | are often not well-supported (Linux doesn't allow them on normal files |
77 | 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 |
78 | files currently, for example), and they would only support aio_read and |
18 | aio_write, so the remaining functionality would have to be implemented |
79 | aio_write, so the remaining functionality would have to be implemented |
19 | using threads anyway. |
80 | using threads anyway. |
20 | |
81 | |
21 | Although the module will work with in the presence of other threads, it |
82 | Although the module will work in the presence of other (Perl-) threads, |
22 | is currently not reentrant, so use appropriate locking yourself. |
83 | it is currently not reentrant in any way, so use appropriate locking |
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84 | yourself, always call "poll_cb" from within the same thread, or never |
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85 | call "poll_cb" (or other "aio_" functions) recursively. |
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86 | |
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87 | EXAMPLE |
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88 | This is a simple example that uses the Event module and loads |
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89 | /etc/passwd asynchronously: |
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90 | |
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91 | use Fcntl; |
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92 | use Event; |
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93 | use IO::AIO; |
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94 | |
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95 | # register the IO::AIO callback with Event |
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96 | Event->io (fd => IO::AIO::poll_fileno, |
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97 | poll => 'r', |
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98 | cb => \&IO::AIO::poll_cb); |
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99 | |
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100 | # queue the request to open /etc/passwd |
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101 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
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102 | my $fh = shift |
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103 | or die "error while opening: $!"; |
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104 | |
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105 | # stat'ing filehandles is generally non-blocking |
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106 | my $size = -s $fh; |
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107 | |
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108 | # queue a request to read the file |
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109 | my $contents; |
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110 | aio_read $fh, 0, $size, $contents, 0, sub { |
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111 | $_[0] == $size |
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112 | or die "short read: $!"; |
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113 | |
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114 | close $fh; |
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115 | |
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116 | # file contents now in $contents |
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117 | print $contents; |
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118 | |
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119 | # exit event loop and program |
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120 | Event::unloop; |
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121 | }; |
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122 | }; |
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123 | |
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124 | # possibly queue up other requests, or open GUI windows, |
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125 | # check for sockets etc. etc. |
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126 | |
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127 | # process events as long as there are some: |
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128 | Event::loop; |
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129 | |
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130 | REQUEST ANATOMY AND LIFETIME |
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131 | Every "aio_*" function creates a request. which is a C data structure |
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132 | not directly visible to Perl. |
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133 | |
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134 | If called in non-void context, every request function returns a Perl |
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135 | object representing the request. In void context, nothing is returned, |
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136 | which saves a bit of memory. |
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137 | |
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138 | The perl object is a fairly standard ref-to-hash object. The hash |
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139 | contents are not used by IO::AIO so you are free to store anything you |
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140 | like in it. |
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141 | |
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142 | During their existance, aio requests travel through the following |
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143 | states, in order: |
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144 | |
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145 | ready |
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146 | Immediately after a request is created it is put into the ready |
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147 | state, waiting for a thread to execute it. |
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148 | |
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149 | execute |
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150 | A thread has accepted the request for processing and is currently |
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151 | executing it (e.g. blocking in read). |
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152 | |
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153 | pending |
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154 | The request has been executed and is waiting for result processing. |
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155 | |
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156 | While request submission and execution is fully asynchronous, result |
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157 | processing is not and relies on the perl interpreter calling |
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158 | "poll_cb" (or another function with the same effect). |
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159 | |
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160 | result |
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161 | The request results are processed synchronously by "poll_cb". |
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162 | |
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163 | The "poll_cb" function will process all outstanding aio requests by |
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164 | calling their callbacks, freeing memory associated with them and |
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165 | managing any groups they are contained in. |
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166 | |
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167 | done |
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168 | Request has reached the end of its lifetime and holds no resources |
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169 | anymore (except possibly for the Perl object, but its connection to |
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170 | the actual aio request is severed and calling its methods will |
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171 | either do nothing or result in a runtime error). |
23 | |
172 | |
24 | FUNCTIONS |
173 | FUNCTIONS |
25 | AIO FUNCTIONS |
174 | AIO REQUEST FUNCTIONS |
26 | All the "aio_*" calls are more or less thin wrappers around the syscall |
175 | 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 |
176 | with the same name (sans "aio_"). The arguments are similar or |
28 | identical, and they all accept an additional $callback argument which |
177 | identical, and they all accept an additional (and optional) $callback |
29 | must be a code reference. This code reference will get called with the |
178 | 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, |
179 | 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 |
180 | error, unlike perl, which usually delivers "false") as it's sole |
32 | syscall has been executed asynchronously. |
181 | argument when the given syscall has been executed asynchronously. |
33 | |
182 | |
34 | All functions that expect a filehandle will also accept a file |
183 | All functions expecting a filehandle keep a copy of the filehandle |
35 | descriptor. |
184 | internally until the request has finished. |
36 | |
185 | |
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186 | All functions return request objects of type IO::AIO::REQ that allow |
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187 | further manipulation of those requests while they are in-flight. |
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188 | |
37 | The filenames you pass to these routines *must* be absolute. The reason |
189 | 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 |
190 | as octets. The reason for the former is that at the time the request is |
39 | directory could have changed. Alternatively, you can make sure that you |
191 | being executed, the current working directory could have changed. |
40 | never change the current working directory. |
192 | Alternatively, you can make sure that you never change the current |
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193 | working directory anywhere in the program and then use relative paths. |
41 | |
194 | |
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195 | To encode pathnames as octets, either make sure you either: a) always |
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196 | pass in filenames you got from outside (command line, readdir etc.) |
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197 | without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module |
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198 | and encode your pathnames to the locale (or other) encoding in effect in |
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199 | the user environment, d) use Glib::filename_from_unicode on unicode |
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200 | filenames or e) use something else to ensure your scalar has the correct |
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201 | contents. |
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202 | |
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203 | This works, btw. independent of the internal UTF-8 bit, which IO::AIO |
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204 | handles correctly wether it is set or not. |
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205 | |
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206 | $prev_pri = aioreq_pri [$pri] |
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207 | Returns the priority value that would be used for the next request |
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208 | and, if $pri is given, sets the priority for the next aio request. |
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209 | |
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210 | The default priority is 0, the minimum and maximum priorities are -4 |
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211 | and 4, respectively. Requests with higher priority will be serviced |
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212 | first. |
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213 | |
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214 | The priority will be reset to 0 after each call to one of the |
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215 | "aio_*" functions. |
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216 | |
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217 | Example: open a file with low priority, then read something from it |
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218 | with higher priority so the read request is serviced before other |
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219 | low priority open requests (potentially spamming the cache): |
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220 | |
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221 | aioreq_pri -3; |
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222 | aio_open ..., sub { |
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223 | return unless $_[0]; |
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224 | |
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225 | aioreq_pri -2; |
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226 | aio_read $_[0], ..., sub { |
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227 | ... |
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228 | }; |
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229 | }; |
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230 | |
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231 | aioreq_nice $pri_adjust |
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232 | Similar to "aioreq_pri", but subtracts the given value from the |
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233 | current priority, so the effect is cumulative. |
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234 | |
42 | aio_open $pathname, $flags, $mode, $callback |
235 | aio_open $pathname, $flags, $mode, $callback->($fh) |
43 | Asynchronously open or create a file and call the callback with a |
236 | Asynchronously open or create a file and call the callback with a |
44 | newly created filehandle for the file. |
237 | newly created filehandle for the file. |
45 | |
238 | |
46 | The pathname passed to "aio_open" must be absolute. See API NOTES, |
239 | The pathname passed to "aio_open" must be absolute. See API NOTES, |
47 | above, for an explanation. |
240 | above, for an explanation. |
48 | |
241 | |
49 | The $mode argument is a bitmask. See the "Fcntl" module for a list. |
242 | The $flags argument is a bitmask. See the "Fcntl" module for a list. |
50 | They are the same as used in "sysopen". |
243 | They are the same as used by "sysopen". |
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244 | |
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245 | Likewise, $mode specifies the mode of the newly created file, if it |
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246 | didn't exist and "O_CREAT" has been given, just like perl's |
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247 | "sysopen", except that it is mandatory (i.e. use 0 if you don't |
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248 | create new files, and 0666 or 0777 if you do). Note that the $mode |
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249 | will be modified by the umask in effect then the request is being |
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250 | executed, so better never change the umask. |
51 | |
251 | |
52 | Example: |
252 | Example: |
53 | |
253 | |
54 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
254 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
55 | if ($_[0]) { |
255 | if ($_[0]) { |
… | |
… | |
58 | } else { |
258 | } else { |
59 | die "open failed: $!\n"; |
259 | die "open failed: $!\n"; |
60 | } |
260 | } |
61 | }; |
261 | }; |
62 | |
262 | |
63 | aio_close $fh, $callback |
263 | aio_close $fh, $callback->($status) |
64 | Asynchronously close a file and call the callback with the result |
264 | Asynchronously close a file and call the callback with the result |
65 | code. *WARNING:* although accepted, you should not pass in a perl |
265 | code. |
66 | filehandle here, as perl will likely close the file descriptor |
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67 | itself when the filehandle is destroyed. Normally, you can safely |
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68 | call perls "close" or just let filehandles go out of scope. |
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69 | |
266 | |
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267 | Unfortunately, you can't do this to perl. Perl *insists* very |
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268 | strongly on closing the file descriptor associated with the |
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269 | filehandle itself. |
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270 | |
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271 | Therefore, "aio_close" will not close the filehandle - instead it |
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272 | will use dup2 to overwrite the file descriptor with the write-end of |
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273 | a pipe (the pipe fd will be created on demand and will be cached). |
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274 | |
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275 | Or in other words: the file descriptor will be closed, but it will |
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276 | not be free for reuse until the perl filehandle is closed. |
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277 | |
70 | aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
278 | aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
71 | aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
279 | aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
72 | Reads or writes "length" bytes from the specified "fh" and "offset" |
280 | Reads or writes $length bytes from the specified $fh and $offset |
73 | into the scalar given by "data" and offset "dataoffset" and calls |
281 | into the scalar given by $data and offset $dataoffset and calls the |
74 | the callback without the actual number of bytes read (or -1 on |
282 | callback without the actual number of bytes read (or -1 on error, |
75 | error, just like the syscall). |
283 | just like the syscall). |
76 | |
284 | |
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285 | If $offset is undefined, then the current file descriptor offset |
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286 | will be used (and updated), otherwise the file descriptor offset |
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287 | will not be changed by these calls. |
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288 | |
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289 | If $length is undefined in "aio_write", use the remaining length of |
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290 | $data. |
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291 | |
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292 | If $dataoffset is less than zero, it will be counted from the end of |
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293 | $data. |
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294 | |
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295 | The $data scalar *MUST NOT* be modified in any way while the request |
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296 | is outstanding. Modifying it can result in segfaults or World War |
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297 | III (if the necessary/optional hardware is installed). |
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298 | |
77 | Example: Read 15 bytes at offset 7 into scalar $buffer, strating at |
299 | Example: Read 15 bytes at offset 7 into scalar $buffer, starting at |
78 | offset 0 within the scalar: |
300 | offset 0 within the scalar: |
79 | |
301 | |
80 | aio_read $fh, 7, 15, $buffer, 0, sub { |
302 | aio_read $fh, 7, 15, $buffer, 0, sub { |
81 | $_[0] >= 0 or die "read error: $!"; |
303 | $_[0] > 0 or die "read error: $!"; |
82 | print "read <$buffer>\n"; |
304 | print "read $_[0] bytes: <$buffer>\n"; |
83 | }; |
305 | }; |
84 | |
306 | |
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307 | aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) |
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308 | Tries to copy $length bytes from $in_fh to $out_fh. It starts |
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309 | reading at byte offset $in_offset, and starts writing at the current |
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310 | file offset of $out_fh. Because of that, it is not safe to issue |
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311 | more than one "aio_sendfile" per $out_fh, as they will interfere |
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312 | with each other. |
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313 | |
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314 | This call tries to make use of a native "sendfile" syscall to |
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315 | provide zero-copy operation. For this to work, $out_fh should refer |
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316 | to a socket, and $in_fh should refer to mmap'able file. |
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317 | |
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318 | If the native sendfile call fails or is not implemented, it will be |
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319 | emulated, so you can call "aio_sendfile" on any type of filehandle |
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320 | regardless of the limitations of the operating system. |
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321 | |
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322 | Please note, however, that "aio_sendfile" can read more bytes from |
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323 | $in_fh than are written, and there is no way to find out how many |
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324 | bytes have been read from "aio_sendfile" alone, as "aio_sendfile" |
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325 | only provides the number of bytes written to $out_fh. Only if the |
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326 | result value equals $length one can assume that $length bytes have |
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327 | been read. |
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328 | |
85 | aio_readahead $fh,$offset,$length, $callback |
329 | aio_readahead $fh,$offset,$length, $callback->($retval) |
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 |
330 | "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 |
331 | 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 |
332 | $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 |
333 | 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 |
334 | 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 |
335 | 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 |
336 | 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 |
337 | read beyond the end of the file. The current file offset of the file |
98 | is left unchanged. |
338 | is left unchanged. |
99 | |
339 | |
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340 | If that syscall doesn't exist (likely if your OS isn't Linux) it |
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341 | will be emulated by simply reading the data, which would have a |
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342 | similar effect. |
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343 | |
100 | aio_stat $fh_or_path, $callback |
344 | aio_stat $fh_or_path, $callback->($status) |
101 | aio_lstat $fh, $callback |
345 | aio_lstat $fh, $callback->($status) |
102 | Works like perl's "stat" or "lstat" in void context. The callback |
346 | 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 |
347 | will be called after the stat and the results will be available |
104 | using "stat _" or "-s _" etc... |
348 | using "stat _" or "-s _" etc... |
105 | |
349 | |
106 | The pathname passed to "aio_stat" must be absolute. See API NOTES, |
350 | The pathname passed to "aio_stat" must be absolute. See API NOTES, |
… | |
… | |
116 | aio_stat "/etc/passwd", sub { |
360 | aio_stat "/etc/passwd", sub { |
117 | $_[0] and die "stat failed: $!"; |
361 | $_[0] and die "stat failed: $!"; |
118 | print "size is ", -s _, "\n"; |
362 | print "size is ", -s _, "\n"; |
119 | }; |
363 | }; |
120 | |
364 | |
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365 | aio_utime $fh_or_path, $atime, $mtime, $callback->($status) |
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366 | Works like perl's "utime" function (including the special case of |
|
|
367 | $atime and $mtime being undef). Fractional times are supported if |
|
|
368 | the underlying syscalls support them. |
|
|
369 | |
|
|
370 | When called with a pathname, uses utimes(2) if available, otherwise |
|
|
371 | utime(2). If called on a file descriptor, uses futimes(2) if |
|
|
372 | available, otherwise returns ENOSYS, so this is not portable. |
|
|
373 | |
|
|
374 | Examples: |
|
|
375 | |
|
|
376 | # set atime and mtime to current time (basically touch(1)): |
|
|
377 | aio_utime "path", undef, undef; |
|
|
378 | # set atime to current time and mtime to beginning of the epoch: |
|
|
379 | aio_utime "path", time, undef; # undef==0 |
|
|
380 | |
|
|
381 | aio_chown $fh_or_path, $uid, $gid, $callback->($status) |
|
|
382 | Works like perl's "chown" function, except that "undef" for either |
|
|
383 | $uid or $gid is being interpreted as "do not change" (but -1 can |
|
|
384 | also be used). |
|
|
385 | |
|
|
386 | Examples: |
|
|
387 | |
|
|
388 | # same as "chown root path" in the shell: |
|
|
389 | aio_chown "path", 0, -1; |
|
|
390 | # same as above: |
|
|
391 | aio_chown "path", 0, undef; |
|
|
392 | |
|
|
393 | aio_truncate $fh_or_path, $offset, $callback->($status) |
|
|
394 | Works like truncate(2) or ftruncate(2). |
|
|
395 | |
|
|
396 | aio_chmod $fh_or_path, $mode, $callback->($status) |
|
|
397 | Works like perl's "chmod" function. |
|
|
398 | |
121 | aio_unlink $pathname, $callback |
399 | aio_unlink $pathname, $callback->($status) |
122 | Asynchronously unlink (delete) a file and call the callback with the |
400 | Asynchronously unlink (delete) a file and call the callback with the |
123 | result code. |
401 | result code. |
124 | |
402 | |
|
|
403 | aio_mknod $path, $mode, $dev, $callback->($status) |
|
|
404 | [EXPERIMENTAL] |
|
|
405 | |
|
|
406 | Asynchronously create a device node (or fifo). See mknod(2). |
|
|
407 | |
|
|
408 | The only (POSIX-) portable way of calling this function is: |
|
|
409 | |
|
|
410 | aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... |
|
|
411 | |
|
|
412 | aio_link $srcpath, $dstpath, $callback->($status) |
|
|
413 | Asynchronously create a new link to the existing object at $srcpath |
|
|
414 | at the path $dstpath and call the callback with the result code. |
|
|
415 | |
|
|
416 | aio_symlink $srcpath, $dstpath, $callback->($status) |
|
|
417 | Asynchronously create a new symbolic link to the existing object at |
|
|
418 | $srcpath at the path $dstpath and call the callback with the result |
|
|
419 | code. |
|
|
420 | |
|
|
421 | aio_readlink $path, $callback->($link) |
|
|
422 | Asynchronously read the symlink specified by $path and pass it to |
|
|
423 | the callback. If an error occurs, nothing or undef gets passed to |
|
|
424 | the callback. |
|
|
425 | |
|
|
426 | aio_rename $srcpath, $dstpath, $callback->($status) |
|
|
427 | Asynchronously rename the object at $srcpath to $dstpath, just as |
|
|
428 | rename(2) and call the callback with the result code. |
|
|
429 | |
|
|
430 | aio_mkdir $pathname, $mode, $callback->($status) |
|
|
431 | Asynchronously mkdir (create) a directory and call the callback with |
|
|
432 | the result code. $mode will be modified by the umask at the time the |
|
|
433 | request is executed, so do not change your umask. |
|
|
434 | |
|
|
435 | aio_rmdir $pathname, $callback->($status) |
|
|
436 | Asynchronously rmdir (delete) a directory and call the callback with |
|
|
437 | the result code. |
|
|
438 | |
|
|
439 | aio_readdir $pathname, $callback->($entries) |
|
|
440 | Unlike the POSIX call of the same name, "aio_readdir" reads an |
|
|
441 | entire directory (i.e. opendir + readdir + closedir). The entries |
|
|
442 | will not be sorted, and will NOT include the "." and ".." entries. |
|
|
443 | |
|
|
444 | The callback a single argument which is either "undef" or an |
|
|
445 | array-ref with the filenames. |
|
|
446 | |
|
|
447 | aio_load $path, $data, $callback->($status) |
|
|
448 | This is a composite request that tries to fully load the given file |
|
|
449 | into memory. Status is the same as with aio_read. |
|
|
450 | |
|
|
451 | aio_copy $srcpath, $dstpath, $callback->($status) |
|
|
452 | Try to copy the *file* (directories not supported as either source |
|
|
453 | or destination) from $srcpath to $dstpath and call the callback with |
|
|
454 | the 0 (error) or -1 ok. |
|
|
455 | |
|
|
456 | This is a composite request that it creates the destination file |
|
|
457 | with mode 0200 and copies the contents of the source file into it |
|
|
458 | using "aio_sendfile", followed by restoring atime, mtime, access |
|
|
459 | mode and uid/gid, in that order. |
|
|
460 | |
|
|
461 | If an error occurs, the partial destination file will be unlinked, |
|
|
462 | if possible, except when setting atime, mtime, access mode and |
|
|
463 | uid/gid, where errors are being ignored. |
|
|
464 | |
|
|
465 | aio_move $srcpath, $dstpath, $callback->($status) |
|
|
466 | Try to move the *file* (directories not supported as either source |
|
|
467 | or destination) from $srcpath to $dstpath and call the callback with |
|
|
468 | the 0 (error) or -1 ok. |
|
|
469 | |
|
|
470 | This is a composite request that tries to rename(2) the file first. |
|
|
471 | If rename files with "EXDEV", it copies the file with "aio_copy" |
|
|
472 | and, if that is successful, unlinking the $srcpath. |
|
|
473 | |
|
|
474 | aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) |
|
|
475 | Scans a directory (similar to "aio_readdir") but additionally tries |
|
|
476 | to efficiently separate the entries of directory $path into two sets |
|
|
477 | of names, directories you can recurse into (directories), and ones |
|
|
478 | you cannot recurse into (everything else, including symlinks to |
|
|
479 | directories). |
|
|
480 | |
|
|
481 | "aio_scandir" is a composite request that creates of many sub |
|
|
482 | requests_ $maxreq specifies the maximum number of outstanding aio |
|
|
483 | requests that this function generates. If it is "<= 0", then a |
|
|
484 | suitable default will be chosen (currently 4). |
|
|
485 | |
|
|
486 | On error, the callback is called without arguments, otherwise it |
|
|
487 | receives two array-refs with path-relative entry names. |
|
|
488 | |
|
|
489 | Example: |
|
|
490 | |
|
|
491 | aio_scandir $dir, 0, sub { |
|
|
492 | my ($dirs, $nondirs) = @_; |
|
|
493 | print "real directories: @$dirs\n"; |
|
|
494 | print "everything else: @$nondirs\n"; |
|
|
495 | }; |
|
|
496 | |
|
|
497 | Implementation notes. |
|
|
498 | |
|
|
499 | The "aio_readdir" cannot be avoided, but "stat()"'ing every entry |
|
|
500 | can. |
|
|
501 | |
|
|
502 | After reading the directory, the modification time, size etc. of the |
|
|
503 | directory before and after the readdir is checked, and if they match |
|
|
504 | (and isn't the current time), the link count will be used to decide |
|
|
505 | how many entries are directories (if >= 2). Otherwise, no knowledge |
|
|
506 | of the number of subdirectories will be assumed. |
|
|
507 | |
|
|
508 | Then entries will be sorted into likely directories (everything |
|
|
509 | without a non-initial dot currently) and likely non-directories |
|
|
510 | (everything else). Then every entry plus an appended "/." will be |
|
|
511 | "stat"'ed, likely directories first. If that succeeds, it assumes |
|
|
512 | that the entry is a directory or a symlink to directory (which will |
|
|
513 | be checked seperately). This is often faster than stat'ing the entry |
|
|
514 | itself because filesystems might detect the type of the entry |
|
|
515 | without reading the inode data (e.g. ext2fs filetype feature). |
|
|
516 | |
|
|
517 | If the known number of directories (link count - 2) has been |
|
|
518 | reached, the rest of the entries is assumed to be non-directories. |
|
|
519 | |
|
|
520 | This only works with certainty on POSIX (= UNIX) filesystems, which |
|
|
521 | fortunately are the vast majority of filesystems around. |
|
|
522 | |
|
|
523 | It will also likely work on non-POSIX filesystems with reduced |
|
|
524 | efficiency as those tend to return 0 or 1 as link counts, which |
|
|
525 | disables the directory counting heuristic. |
|
|
526 | |
|
|
527 | aio_rmtree $path, $callback->($status) |
|
|
528 | Delete a directory tree starting (and including) $path, return the |
|
|
529 | status of the final "rmdir" only. This is a composite request that |
|
|
530 | uses "aio_scandir" to recurse into and rmdir directories, and unlink |
|
|
531 | everything else. |
|
|
532 | |
|
|
533 | aio_sync $callback->($status) |
|
|
534 | Asynchronously call sync and call the callback when finished. |
|
|
535 | |
125 | aio_fsync $fh, $callback |
536 | aio_fsync $fh, $callback->($status) |
126 | Asynchronously call fsync on the given filehandle and call the |
537 | Asynchronously call fsync on the given filehandle and call the |
127 | callback with the fsync result code. |
538 | callback with the fsync result code. |
128 | |
539 | |
129 | aio_fdatasync $fh, $callback |
540 | aio_fdatasync $fh, $callback->($status) |
130 | Asynchronously call fdatasync on the given filehandle and call the |
541 | Asynchronously call fdatasync on the given filehandle and call the |
131 | callback with the fdatasync result code. |
542 | callback with the fdatasync result code. |
132 | |
543 | |
|
|
544 | If this call isn't available because your OS lacks it or it couldn't |
|
|
545 | be detected, it will be emulated by calling "fsync" instead. |
|
|
546 | |
|
|
547 | aio_pathsync $path, $callback->($status) |
|
|
548 | This request tries to open, fsync and close the given path. This is |
|
|
549 | a composite request intended tosync directories after directory |
|
|
550 | operations (E.g. rename). This might not work on all operating |
|
|
551 | systems or have any specific effect, but usually it makes sure that |
|
|
552 | directory changes get written to disc. It works for anything that |
|
|
553 | can be opened for read-only, not just directories. |
|
|
554 | |
|
|
555 | Passes 0 when everything went ok, and -1 on error. |
|
|
556 | |
|
|
557 | aio_group $callback->(...) |
|
|
558 | This is a very special aio request: Instead of doing something, it |
|
|
559 | is a container for other aio requests, which is useful if you want |
|
|
560 | to bundle many requests into a single, composite, request with a |
|
|
561 | definite callback and the ability to cancel the whole request with |
|
|
562 | its subrequests. |
|
|
563 | |
|
|
564 | Returns an object of class IO::AIO::GRP. See its documentation below |
|
|
565 | for more info. |
|
|
566 | |
|
|
567 | Example: |
|
|
568 | |
|
|
569 | my $grp = aio_group sub { |
|
|
570 | print "all stats done\n"; |
|
|
571 | }; |
|
|
572 | |
|
|
573 | add $grp |
|
|
574 | (aio_stat ...), |
|
|
575 | (aio_stat ...), |
|
|
576 | ...; |
|
|
577 | |
|
|
578 | aio_nop $callback->() |
|
|
579 | This is a special request - it does nothing in itself and is only |
|
|
580 | used for side effects, such as when you want to add a dummy request |
|
|
581 | to a group so that finishing the requests in the group depends on |
|
|
582 | executing the given code. |
|
|
583 | |
|
|
584 | While this request does nothing, it still goes through the execution |
|
|
585 | phase and still requires a worker thread. Thus, the callback will |
|
|
586 | not be executed immediately but only after other requests in the |
|
|
587 | queue have entered their execution phase. This can be used to |
|
|
588 | measure request latency. |
|
|
589 | |
|
|
590 | IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED* |
|
|
591 | Mainly used for debugging and benchmarking, this aio request puts |
|
|
592 | one of the request workers to sleep for the given time. |
|
|
593 | |
|
|
594 | While it is theoretically handy to have simple I/O scheduling |
|
|
595 | requests like sleep and file handle readable/writable, the overhead |
|
|
596 | this creates is immense (it blocks a thread for a long time) so do |
|
|
597 | not use this function except to put your application under |
|
|
598 | artificial I/O pressure. |
|
|
599 | |
|
|
600 | IO::AIO::REQ CLASS |
|
|
601 | All non-aggregate "aio_*" functions return an object of this class when |
|
|
602 | called in non-void context. |
|
|
603 | |
|
|
604 | cancel $req |
|
|
605 | Cancels the request, if possible. Has the effect of skipping |
|
|
606 | execution when entering the execute state and skipping calling the |
|
|
607 | callback when entering the the result state, but will leave the |
|
|
608 | request otherwise untouched. That means that requests that currently |
|
|
609 | execute will not be stopped and resources held by the request will |
|
|
610 | not be freed prematurely. |
|
|
611 | |
|
|
612 | cb $req $callback->(...) |
|
|
613 | Replace (or simply set) the callback registered to the request. |
|
|
614 | |
|
|
615 | IO::AIO::GRP CLASS |
|
|
616 | This class is a subclass of IO::AIO::REQ, so all its methods apply to |
|
|
617 | objects of this class, too. |
|
|
618 | |
|
|
619 | A IO::AIO::GRP object is a special request that can contain multiple |
|
|
620 | other aio requests. |
|
|
621 | |
|
|
622 | You create one by calling the "aio_group" constructing function with a |
|
|
623 | callback that will be called when all contained requests have entered |
|
|
624 | the "done" state: |
|
|
625 | |
|
|
626 | my $grp = aio_group sub { |
|
|
627 | print "all requests are done\n"; |
|
|
628 | }; |
|
|
629 | |
|
|
630 | You add requests by calling the "add" method with one or more |
|
|
631 | "IO::AIO::REQ" objects: |
|
|
632 | |
|
|
633 | $grp->add (aio_unlink "..."); |
|
|
634 | |
|
|
635 | add $grp aio_stat "...", sub { |
|
|
636 | $_[0] or return $grp->result ("error"); |
|
|
637 | |
|
|
638 | # add another request dynamically, if first succeeded |
|
|
639 | add $grp aio_open "...", sub { |
|
|
640 | $grp->result ("ok"); |
|
|
641 | }; |
|
|
642 | }; |
|
|
643 | |
|
|
644 | This makes it very easy to create composite requests (see the source of |
|
|
645 | "aio_move" for an application) that work and feel like simple requests. |
|
|
646 | |
|
|
647 | * The IO::AIO::GRP objects will be cleaned up during calls to |
|
|
648 | "IO::AIO::poll_cb", just like any other request. |
|
|
649 | |
|
|
650 | * They can be canceled like any other request. Canceling will cancel |
|
|
651 | not only the request itself, but also all requests it contains. |
|
|
652 | |
|
|
653 | * They can also can also be added to other IO::AIO::GRP objects. |
|
|
654 | |
|
|
655 | * You must not add requests to a group from within the group callback |
|
|
656 | (or any later time). |
|
|
657 | |
|
|
658 | Their lifetime, simplified, looks like this: when they are empty, they |
|
|
659 | will finish very quickly. If they contain only requests that are in the |
|
|
660 | "done" state, they will also finish. Otherwise they will continue to |
|
|
661 | exist. |
|
|
662 | |
|
|
663 | That means after creating a group you have some time to add requests. |
|
|
664 | And in the callbacks of those requests, you can add further requests to |
|
|
665 | the group. And only when all those requests have finished will the the |
|
|
666 | group itself finish. |
|
|
667 | |
|
|
668 | add $grp ... |
|
|
669 | $grp->add (...) |
|
|
670 | Add one or more requests to the group. Any type of IO::AIO::REQ can |
|
|
671 | be added, including other groups, as long as you do not create |
|
|
672 | circular dependencies. |
|
|
673 | |
|
|
674 | Returns all its arguments. |
|
|
675 | |
|
|
676 | $grp->cancel_subs |
|
|
677 | Cancel all subrequests and clears any feeder, but not the group |
|
|
678 | request itself. Useful when you queued a lot of events but got a |
|
|
679 | result early. |
|
|
680 | |
|
|
681 | $grp->result (...) |
|
|
682 | Set the result value(s) that will be passed to the group callback |
|
|
683 | when all subrequests have finished and set the groups errno to the |
|
|
684 | current value of errno (just like calling "errno" without an error |
|
|
685 | number). By default, no argument will be passed and errno is zero. |
|
|
686 | |
|
|
687 | $grp->errno ([$errno]) |
|
|
688 | Sets the group errno value to $errno, or the current value of errno |
|
|
689 | when the argument is missing. |
|
|
690 | |
|
|
691 | Every aio request has an associated errno value that is restored |
|
|
692 | when the callback is invoked. This method lets you change this value |
|
|
693 | from its default (0). |
|
|
694 | |
|
|
695 | Calling "result" will also set errno, so make sure you either set $! |
|
|
696 | before the call to "result", or call c<errno> after it. |
|
|
697 | |
|
|
698 | feed $grp $callback->($grp) |
|
|
699 | Sets a feeder/generator on this group: every group can have an |
|
|
700 | attached generator that generates requests if idle. The idea behind |
|
|
701 | this is that, although you could just queue as many requests as you |
|
|
702 | want in a group, this might starve other requests for a potentially |
|
|
703 | long time. For example, "aio_scandir" might generate hundreds of |
|
|
704 | thousands "aio_stat" requests, delaying any later requests for a |
|
|
705 | long time. |
|
|
706 | |
|
|
707 | To avoid this, and allow incremental generation of requests, you can |
|
|
708 | instead a group and set a feeder on it that generates those |
|
|
709 | requests. The feed callback will be called whenever there are few |
|
|
710 | enough (see "limit", below) requests active in the group itself and |
|
|
711 | is expected to queue more requests. |
|
|
712 | |
|
|
713 | The feed callback can queue as many requests as it likes (i.e. "add" |
|
|
714 | does not impose any limits). |
|
|
715 | |
|
|
716 | If the feed does not queue more requests when called, it will be |
|
|
717 | automatically removed from the group. |
|
|
718 | |
|
|
719 | If the feed limit is 0, it will be set to 2 automatically. |
|
|
720 | |
|
|
721 | Example: |
|
|
722 | |
|
|
723 | # stat all files in @files, but only ever use four aio requests concurrently: |
|
|
724 | |
|
|
725 | my $grp = aio_group sub { print "finished\n" }; |
|
|
726 | limit $grp 4; |
|
|
727 | feed $grp sub { |
|
|
728 | my $file = pop @files |
|
|
729 | or return; |
|
|
730 | |
|
|
731 | add $grp aio_stat $file, sub { ... }; |
|
|
732 | }; |
|
|
733 | |
|
|
734 | limit $grp $num |
|
|
735 | Sets the feeder limit for the group: The feeder will be called |
|
|
736 | whenever the group contains less than this many requests. |
|
|
737 | |
|
|
738 | Setting the limit to 0 will pause the feeding process. |
|
|
739 | |
133 | SUPPORT FUNCTIONS |
740 | SUPPORT FUNCTIONS |
|
|
741 | EVENT PROCESSING AND EVENT LOOP INTEGRATION |
134 | $fileno = IO::AIO::poll_fileno |
742 | $fileno = IO::AIO::poll_fileno |
135 | Return the *request result pipe filehandle*. This filehandle must be |
743 | Return the *request result pipe file descriptor*. This filehandle |
136 | polled for reading by some mechanism outside this module (e.g. Event |
744 | 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 |
745 | (e.g. Event or select, see below or the SYNOPSIS). If the pipe |
138 | "poll_cb" to check the results. |
746 | becomes readable you have to call "poll_cb" to check the results. |
139 | |
747 | |
140 | See "poll_cb" for an example. |
748 | See "poll_cb" for an example. |
141 | |
749 | |
142 | IO::AIO::poll_cb |
750 | IO::AIO::poll_cb |
143 | Process all outstanding events on the result pipe. You have to call |
751 | Process some outstanding events on the result pipe. You have to call |
144 | this regularly. Returns the number of events processed. Returns |
752 | this regularly. Returns 0 if all events could be processed, or -1 if |
145 | immediately when no events are outstanding. |
753 | it returned earlier for whatever reason. Returns immediately when no |
|
|
754 | events are outstanding. The amount of events processed depends on |
|
|
755 | the settings of "IO::AIO::max_poll_req" and |
|
|
756 | "IO::AIO::max_poll_time". |
146 | |
757 | |
147 | You can use Event to multiplex, e.g.: |
758 | If not all requests were processed for whatever reason, the |
|
|
759 | filehandle will still be ready when "poll_cb" returns, so normally |
|
|
760 | you don't have to do anything special to have it called later. |
|
|
761 | |
|
|
762 | Example: Install an Event watcher that automatically calls |
|
|
763 | IO::AIO::poll_cb with high priority: |
148 | |
764 | |
149 | Event->io (fd => IO::AIO::poll_fileno, |
765 | Event->io (fd => IO::AIO::poll_fileno, |
150 | poll => 'r', async => 1, |
766 | poll => 'r', async => 1, |
151 | cb => \&IO::AIO::poll_cb); |
767 | cb => \&IO::AIO::poll_cb); |
152 | |
768 | |
|
|
769 | IO::AIO::max_poll_reqs $nreqs |
|
|
770 | IO::AIO::max_poll_time $seconds |
|
|
771 | These set the maximum number of requests (default 0, meaning |
|
|
772 | infinity) that are being processed by "IO::AIO::poll_cb" in one |
|
|
773 | call, respectively the maximum amount of time (default 0, meaning |
|
|
774 | infinity) spent in "IO::AIO::poll_cb" to process requests (more |
|
|
775 | correctly the mininum amount of time "poll_cb" is allowed to use). |
|
|
776 | |
|
|
777 | Setting "max_poll_time" to a non-zero value creates an overhead of |
|
|
778 | one syscall per request processed, which is not normally a problem |
|
|
779 | unless your callbacks are really really fast or your OS is really |
|
|
780 | really slow (I am not mentioning Solaris here). Using |
|
|
781 | "max_poll_reqs" incurs no overhead. |
|
|
782 | |
|
|
783 | Setting these is useful if you want to ensure some level of |
|
|
784 | interactiveness when perl is not fast enough to process all requests |
|
|
785 | in time. |
|
|
786 | |
|
|
787 | For interactive programs, values such as 0.01 to 0.1 should be fine. |
|
|
788 | |
|
|
789 | Example: Install an Event watcher that automatically calls |
|
|
790 | IO::AIO::poll_cb with low priority, to ensure that other parts of |
|
|
791 | the program get the CPU sometimes even under high AIO load. |
|
|
792 | |
|
|
793 | # try not to spend much more than 0.1s in poll_cb |
|
|
794 | IO::AIO::max_poll_time 0.1; |
|
|
795 | |
|
|
796 | # use a low priority so other tasks have priority |
|
|
797 | Event->io (fd => IO::AIO::poll_fileno, |
|
|
798 | poll => 'r', nice => 1, |
|
|
799 | cb => &IO::AIO::poll_cb); |
|
|
800 | |
153 | IO::AIO::poll_wait |
801 | IO::AIO::poll_wait |
|
|
802 | If there are any outstanding requests and none of them in the result |
154 | Wait till the result filehandle becomes ready for reading (simply |
803 | phase, wait till the result filehandle becomes ready for reading |
155 | does a select on the filehandle. This is useful if you want to |
804 | (simply does a "select" on the filehandle. This is useful if you |
156 | synchronously wait for some requests to finish). |
805 | want to synchronously wait for some requests to finish). |
157 | |
806 | |
158 | See "nreqs" for an example. |
807 | See "nreqs" for an example. |
159 | |
808 | |
|
|
809 | IO::AIO::poll |
|
|
810 | Waits until some requests have been handled. |
|
|
811 | |
|
|
812 | Returns the number of requests processed, but is otherwise strictly |
|
|
813 | equivalent to: |
|
|
814 | |
|
|
815 | IO::AIO::poll_wait, IO::AIO::poll_cb |
|
|
816 | |
160 | IO::AIO::nreqs |
817 | IO::AIO::flush |
161 | Returns the number of requests currently outstanding. |
818 | Wait till all outstanding AIO requests have been handled. |
162 | |
819 | |
163 | Example: wait till there are no outstanding requests anymore: |
820 | Strictly equivalent to: |
164 | |
821 | |
165 | IO::AIO::poll_wait, IO::AIO::poll_cb |
822 | IO::AIO::poll_wait, IO::AIO::poll_cb |
166 | while IO::AIO::nreqs; |
823 | while IO::AIO::nreqs; |
167 | |
824 | |
|
|
825 | CONTROLLING THE NUMBER OF THREADS |
168 | IO::AIO::min_parallel $nthreads |
826 | IO::AIO::min_parallel $nthreads |
169 | Set the minimum number of AIO threads to $nthreads. The default is |
827 | Set the minimum number of AIO threads to $nthreads. The current |
170 | 1, which means a single asynchronous operation can be done at one |
828 | default is 8, which means eight asynchronous operations can execute |
171 | time (the number of outstanding operations, however, is unlimited). |
829 | concurrently at any one time (the number of outstanding requests, |
|
|
830 | however, is unlimited). |
172 | |
831 | |
|
|
832 | IO::AIO starts threads only on demand, when an AIO request is queued |
|
|
833 | and no free thread exists. Please note that queueing up a hundred |
|
|
834 | requests can create demand for a hundred threads, even if it turns |
|
|
835 | out that everything is in the cache and could have been processed |
|
|
836 | faster by a single thread. |
|
|
837 | |
173 | It is recommended to keep the number of threads low, as some Linux |
838 | It is recommended to keep the number of threads relatively low, as |
174 | kernel versions will scale negatively with the number of threads |
839 | some Linux kernel versions will scale negatively with the number of |
175 | (higher parallelity => MUCH higher latency). With current Linux 2.6 |
840 | threads (higher parallelity => MUCH higher latency). With current |
176 | versions, 4-32 threads should be fine. |
841 | Linux 2.6 versions, 4-32 threads should be fine. |
177 | |
842 | |
178 | Under normal circumstances you don't need to call this function, as |
843 | Under most circumstances you don't need to call this function, as |
179 | this module automatically starts some threads (the exact number |
844 | the module selects a default that is suitable for low to moderate |
180 | might change, and is currently 4). |
845 | load. |
181 | |
846 | |
182 | IO::AIO::max_parallel $nthreads |
847 | IO::AIO::max_parallel $nthreads |
183 | Sets the maximum number of AIO threads to $nthreads. If more than |
848 | Sets the maximum number of AIO threads to $nthreads. If more than |
184 | the specified number of threads are currently running, kill them. |
849 | the specified number of threads are currently running, this function |
185 | This function blocks until the limit is reached. |
850 | kills them. This function blocks until the limit is reached. |
|
|
851 | |
|
|
852 | While $nthreads are zero, aio requests get queued but not executed |
|
|
853 | until the number of threads has been increased again. |
186 | |
854 | |
187 | This module automatically runs "max_parallel 0" at program end, to |
855 | This module automatically runs "max_parallel 0" at program end, to |
188 | ensure that all threads are killed and that there are no outstanding |
856 | ensure that all threads are killed and that there are no outstanding |
189 | requests. |
857 | requests. |
190 | |
858 | |
191 | Under normal circumstances you don't need to call this function. |
859 | Under normal circumstances you don't need to call this function. |
192 | |
860 | |
|
|
861 | IO::AIO::max_idle $nthreads |
|
|
862 | Limit the number of threads (default: 4) that are allowed to idle |
|
|
863 | (i.e., threads that did not get a request to process within 10 |
|
|
864 | seconds). That means if a thread becomes idle while $nthreads other |
|
|
865 | threads are also idle, it will free its resources and exit. |
|
|
866 | |
|
|
867 | This is useful when you allow a large number of threads (e.g. 100 or |
|
|
868 | 1000) to allow for extremely high load situations, but want to free |
|
|
869 | resources under normal circumstances (1000 threads can easily |
|
|
870 | consume 30MB of RAM). |
|
|
871 | |
|
|
872 | The default is probably ok in most situations, especially if thread |
|
|
873 | creation is fast. If thread creation is very slow on your system you |
|
|
874 | might want to use larger values. |
|
|
875 | |
193 | $oldnreqs = IO::AIO::max_outstanding $nreqs |
876 | IO::AIO::max_outstanding $maxreqs |
|
|
877 | This is a very bad function to use in interactive programs because |
|
|
878 | it blocks, and a bad way to reduce concurrency because it is |
|
|
879 | inexact: Better use an "aio_group" together with a feed callback. |
|
|
880 | |
194 | Sets the maximum number of outstanding requests to $nreqs. If you |
881 | Sets the maximum number of outstanding requests to $nreqs. If you do |
195 | try to queue up more than this number of requests, the caller will |
882 | queue up more than this number of requests, the next call to the |
196 | block until some requests have been handled. |
883 | "poll_cb" (and "poll_some" and other functions calling "poll_cb") |
|
|
884 | function will block until the limit is no longer exceeded. |
197 | |
885 | |
198 | The default is very large, so normally there is no practical limit. |
886 | The default value is very large, so there is no practical limit on |
199 | If you queue up many requests in a loop it it often improves speed |
887 | the number of outstanding requests. |
200 | if you set this to a relatively low number, such as 100. |
|
|
201 | |
888 | |
202 | Under normal circumstances you don't need to call this function. |
889 | You can still queue as many requests as you want. Therefore, |
|
|
890 | "max_outstanding" is mainly useful in simple scripts (with low |
|
|
891 | values) or as a stop gap to shield against fatal memory overflow |
|
|
892 | (with large values). |
|
|
893 | |
|
|
894 | STATISTICAL INFORMATION |
|
|
895 | IO::AIO::nreqs |
|
|
896 | Returns the number of requests currently in the ready, execute or |
|
|
897 | pending states (i.e. for which their callback has not been invoked |
|
|
898 | yet). |
|
|
899 | |
|
|
900 | Example: wait till there are no outstanding requests anymore: |
|
|
901 | |
|
|
902 | IO::AIO::poll_wait, IO::AIO::poll_cb |
|
|
903 | while IO::AIO::nreqs; |
|
|
904 | |
|
|
905 | IO::AIO::nready |
|
|
906 | Returns the number of requests currently in the ready state (not yet |
|
|
907 | executed). |
|
|
908 | |
|
|
909 | IO::AIO::npending |
|
|
910 | Returns the number of requests currently in the pending state |
|
|
911 | (executed, but not yet processed by poll_cb). |
|
|
912 | |
|
|
913 | FORK BEHAVIOUR |
|
|
914 | This module should do "the right thing" when the process using it forks: |
|
|
915 | |
|
|
916 | Before the fork, IO::AIO enters a quiescent state where no requests can |
|
|
917 | be added in other threads and no results will be processed. After the |
|
|
918 | fork the parent simply leaves the quiescent state and continues |
|
|
919 | request/result processing, while the child frees the request/result |
|
|
920 | queue (so that the requests started before the fork will only be handled |
|
|
921 | in the parent). Threads will be started on demand until the limit set in |
|
|
922 | the parent process has been reached again. |
|
|
923 | |
|
|
924 | In short: the parent will, after a short pause, continue as if fork had |
|
|
925 | not been called, while the child will act as if IO::AIO has not been |
|
|
926 | used yet. |
|
|
927 | |
|
|
928 | MEMORY USAGE |
|
|
929 | Per-request usage: |
|
|
930 | |
|
|
931 | Each aio request uses - depending on your architecture - around 100-200 |
|
|
932 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
|
|
933 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
|
|
934 | scalars and other data passed into aio requests will also be locked and |
|
|
935 | will consume memory till the request has entered the done state. |
|
|
936 | |
|
|
937 | This is not awfully much, so queuing lots of requests is not usually a |
|
|
938 | problem. |
|
|
939 | |
|
|
940 | Per-thread usage: |
|
|
941 | |
|
|
942 | In the execution phase, some aio requests require more memory for |
|
|
943 | temporary buffers, and each thread requires a stack and other data |
|
|
944 | structures (usually around 16k-128k, depending on the OS). |
|
|
945 | |
|
|
946 | KNOWN BUGS |
|
|
947 | Known bugs will be fixed in the next release. |
203 | |
948 | |
204 | SEE ALSO |
949 | SEE ALSO |
205 | Coro, Linux::AIO. |
950 | AnyEvent::AIO for easy integration into event loops, Coro::AIO for a |
|
|
951 | more natural syntax. |
206 | |
952 | |
207 | AUTHOR |
953 | AUTHOR |
208 | Marc Lehmann <schmorp@schmorp.de> |
954 | Marc Lehmann <schmorp@schmorp.de> |
209 | http://home.schmorp.de/ |
955 | http://home.schmorp.de/ |
210 | |
956 | |