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4 | SYNOPSIS |
4 | SYNOPSIS |
5 | use IO::AIO; |
5 | use IO::AIO; |
6 | |
6 | |
7 | DESCRIPTION |
7 | DESCRIPTION |
8 | This module implements asynchronous I/O using whatever means your |
8 | This module implements asynchronous I/O using whatever means your |
9 | operating system supports. Currently, it falls back to Linux::AIO if |
9 | operating system supports. |
10 | that module is available, or uses pthreads to emulato aio functionality. |
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11 | |
10 | |
12 | Currently, in this module a number of threads are started that execute |
11 | Currently, a number of threads are started that execute your read/writes |
13 | your read/writes and signal their completion. You don't need thread |
12 | and signal their completion. You don't need thread support in your libc |
14 | support in your libc or perl, and the threads created by this module |
13 | or perl, and the threads created by this module will not be visible to |
15 | will not be visible to the pthreads library. |
14 | the pthreads library. In the future, this module might make use of the |
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15 | native aio functions available on many operating systems. However, they |
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16 | are often not well-supported (Linux doesn't allow them on normal files |
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17 | currently, for example), and they would only support aio_read and |
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18 | aio_write, so the remaining functionality would have to be implemented |
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19 | using threads anyway. |
16 | |
20 | |
17 | Although the module will work with in the presence of other threads, it |
21 | Although the module will work with in the presence of other threads, it |
18 | is not reentrant, so use appropriate locking yourself. |
22 | is currently not reentrant, so use appropriate locking yourself. |
19 | |
23 | |
20 | API NOTES |
24 | API NOTES |
21 | All the "aio_*" calls are more or less thin wrappers around the syscall |
25 | All the "aio_*" calls are more or less thin wrappers around the syscall |
22 | with the same name (sans "aio_"). The arguments are similar or |
26 | with the same name (sans "aio_"). The arguments are similar or |
23 | identical, and they all accept an additional $callback argument which |
27 | identical, and they all accept an additional $callback argument which |
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37 | IO::AIO::min_parallel $nthreads |
41 | IO::AIO::min_parallel $nthreads |
38 | Set the minimum number of AIO threads to $nthreads. The default is |
42 | Set the minimum number of AIO threads to $nthreads. The default is |
39 | 1, which means a single asynchronous operation can be done at one |
43 | 1, which means a single asynchronous operation can be done at one |
40 | time (the number of outstanding operations, however, is unlimited). |
44 | time (the number of outstanding operations, however, is unlimited). |
41 | |
45 | |
42 | It is recommended to keep the number of threads low, as some linux |
46 | It is recommended to keep the number of threads low, as some Linux |
43 | kernel versions will scale negatively with the number of threads |
47 | kernel versions will scale negatively with the number of threads |
44 | (higher parallelity => MUCH higher latency). |
48 | (higher parallelity => MUCH higher latency). With current Linux 2.6 |
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49 | versions, 4-32 threads should be fine. |
45 | |
50 | |
46 | Under normal circumstances you don't need to call this function, as |
51 | Under normal circumstances you don't need to call this function, as |
47 | this module automatically starts a single async thread. |
52 | this module automatically starts some threads (the exact number |
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53 | might change, and is currently 4). |
48 | |
54 | |
49 | IO::AIO::max_parallel $nthreads |
55 | IO::AIO::max_parallel $nthreads |
50 | Sets the maximum number of AIO threads to $nthreads. If more than |
56 | Sets the maximum number of AIO threads to $nthreads. If more than |
51 | the specified number of threads are currently running, kill them. |
57 | the specified number of threads are currently running, kill them. |
52 | This function blocks until the limit is reached. |
58 | This function blocks until the limit is reached. |
53 | |
59 | |
54 | This module automatically runs "max_parallel 0" at program end, to |
60 | This module automatically runs "max_parallel 0" at program end, to |
55 | ensure that all threads are killed and that there are no outstanding |
61 | ensure that all threads are killed and that there are no outstanding |
56 | requests. |
62 | requests. |
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63 | |
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64 | Under normal circumstances you don't need to call this function. |
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65 | |
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66 | $oldnreqs = IO::AIO::max_outstanding $nreqs |
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67 | Sets the maximum number of outstanding requests to $nreqs. If you |
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68 | try to queue up more than this number of requests, the caller will |
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69 | block until some requests have been handled. |
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70 | |
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71 | The default is very large, so normally there is no practical limit. |
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72 | If you queue up many requests in a loop it it often improves speed |
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73 | if you set this to a relatively low number, such as 100. |
57 | |
74 | |
58 | Under normal circumstances you don't need to call this function. |
75 | Under normal circumstances you don't need to call this function. |
59 | |
76 | |
60 | $fileno = IO::AIO::poll_fileno |
77 | $fileno = IO::AIO::poll_fileno |
61 | Return the *request result pipe filehandle*. This filehandle must be |
78 | Return the *request result pipe filehandle*. This filehandle must be |
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90 | |
107 | |
91 | IO::AIO::poll_wait, IO::AIO::poll_cb |
108 | IO::AIO::poll_wait, IO::AIO::poll_cb |
92 | while IO::AIO::nreqs; |
109 | while IO::AIO::nreqs; |
93 | |
110 | |
94 | aio_open $pathname, $flags, $mode, $callback |
111 | aio_open $pathname, $flags, $mode, $callback |
95 | Asynchronously open or create a file and call the callback with the |
112 | Asynchronously open or create a file and call the callback with a |
96 | filedescriptor (NOT a perl filehandle, sorry for that, but watch |
113 | newly created filehandle for the file. |
97 | out, this might change in the future). |
114 | |
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115 | The pathname passed to "aio_open" must be absolute. See API NOTES, |
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116 | above, for an explanation. |
98 | |
117 | |
99 | The $mode argument is a bitmask. See the "Fcntl" module for a list. |
118 | The $mode argument is a bitmask. See the "Fcntl" module for a list. |
100 | They are the same as used in "sysopen". |
119 | They are the same as used in "sysopen". |
101 | |
120 | |
102 | Example: |
121 | Example: |
103 | |
122 | |
104 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
123 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
105 | if ($_[0] >= 0) { |
124 | if ($_[0]) { |
106 | open my $fh, "<&$_[0]"; # create a copy for perl |
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107 | aio_close $_[0], sub { }; # close the aio handle |
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108 | print "open successful, fh is $fh\n"; |
125 | print "open successful, fh is $_[0]\n"; |
109 | ... |
126 | ... |
110 | } else { |
127 | } else { |
111 | die "open failed: $!\n"; |
128 | die "open failed: $!\n"; |
112 | } |
129 | } |
113 | }; |
130 | }; |
114 | |
131 | |
115 | aio_close $fh, $callback |
132 | aio_close $fh, $callback |
116 | Asynchronously close a file and call the callback with the result |
133 | Asynchronously close a file and call the callback with the result |
117 | code. |
134 | code. *WARNING:* although accepted, you should not pass in a perl |
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135 | filehandle here, as perl will likely close the file descriptor |
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136 | itself when the filehandle is destroyed. Normally, you can safely |
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137 | call perls "close" or just let filehandles go out of scope. |
118 | |
138 | |
119 | aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
139 | aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
120 | aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
140 | aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
121 | Reads or writes "length" bytes from the specified "fh" and "offset" |
141 | Reads or writes "length" bytes from the specified "fh" and "offset" |
122 | into the scalar given by "data" and offset "dataoffset" and calls |
142 | into the scalar given by "data" and offset "dataoffset" and calls |
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131 | print "read <$buffer>\n"; |
151 | print "read <$buffer>\n"; |
132 | }; |
152 | }; |
133 | |
153 | |
134 | aio_readahead $fh,$offset,$length, $callback |
154 | aio_readahead $fh,$offset,$length, $callback |
135 | Asynchronously reads the specified byte range into the page cache, |
155 | Asynchronously reads the specified byte range into the page cache, |
136 | using the "readahead" syscall. |
156 | using the "readahead" syscall. If that syscall doesn't exist the |
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157 | status will be -1 and $! is set to ENOSYS. |
137 | |
158 | |
138 | readahead() populates the page cache with data from a file so that |
159 | readahead() populates the page cache with data from a file so that |
139 | subsequent reads from that file will not block on disk I/O. The |
160 | subsequent reads from that file will not block on disk I/O. The |
140 | $offset argument specifies the starting point from which data is to |
161 | $offset argument specifies the starting point from which data is to |
141 | be read and $length specifies the number of bytes to be read. I/O is |
162 | be read and $length specifies the number of bytes to be read. I/O is |
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177 | aio_fdatasync $fh, $callback |
198 | aio_fdatasync $fh, $callback |
178 | Asynchronously call fdatasync on the given filehandle and call the |
199 | Asynchronously call fdatasync on the given filehandle and call the |
179 | callback with the fdatasync result code. |
200 | callback with the fdatasync result code. |
180 | |
201 | |
181 | BUGS |
202 | BUGS |
182 | This module has been extensively tested in a large and very busy |
203 | - could be optimized to use more semaphores instead of filehandles. |
183 | webserver for many years now. |
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184 | |
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185 | - aio_open gives a fd, but all other functions expect a perl filehandle. |
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186 | |
204 | |
187 | SEE ALSO |
205 | SEE ALSO |
188 | Coro. |
206 | Coro, Linux::AIO. |
189 | |
207 | |
190 | AUTHOR |
208 | AUTHOR |
191 | Marc Lehmann <schmorp@schmorp.de> |
209 | Marc Lehmann <schmorp@schmorp.de> |
192 | http://home.schmorp.de/ |
210 | http://home.schmorp.de/ |
193 | |
211 | |