1 |
root |
1.1 |
NAME |
2 |
|
|
Linux::AIO - linux-specific aio implemented using clone |
3 |
|
|
|
4 |
|
|
SYNOPSIS |
5 |
|
|
use Linux::AIO; |
6 |
|
|
|
7 |
|
|
DESCRIPTION |
8 |
root |
1.3 |
This module implements asynchronous I/O using the means available to |
9 |
|
|
Linux - clone. It does not hook into the POSIX aio_* functions because |
10 |
|
|
Linux does not yet support these in the kernel (even as of 2.6.12, only |
11 |
|
|
O_DIRECT files are supported) and even if, it would only allow aio_read |
12 |
|
|
and write, not open, stat and so on. |
13 |
root |
1.1 |
|
14 |
|
|
Instead, in this module a number of (non-posix) threads are started that |
15 |
|
|
execute your read/writes and signal their completion. You don't need |
16 |
|
|
thread support in your libc or perl, and the threads created by this |
17 |
|
|
module will not be visible to the pthreads library. |
18 |
|
|
|
19 |
|
|
NOTICE: the threads created by this module will automatically be killed |
20 |
|
|
when the thread calling min_parallel exits. Make sure you only ever call |
21 |
|
|
min_parallel from the same thread that loaded this module. |
22 |
|
|
|
23 |
root |
1.3 |
Although the module will work with in the presence of other threads, it |
24 |
|
|
is not reentrant, so use appropriate locking yourself. |
25 |
root |
1.1 |
|
26 |
root |
1.4 |
API NOTES |
27 |
|
|
All the "aio_*" calls are more or less thin wrappers around the syscall |
28 |
|
|
with the same name (sans "aio_"). The arguments are similar or |
29 |
|
|
identical, and they all accept an additional $callback argument which |
30 |
|
|
must be a code reference. This code reference will get called with the |
31 |
|
|
syscall return code (e.g. most syscalls return -1 on error, unlike perl, |
32 |
|
|
which usually delivers "false") as it's sole argument when the given |
33 |
|
|
syscall has been executed asynchronously. |
34 |
|
|
|
35 |
|
|
All functions that expect a filehandle will also accept a file |
36 |
|
|
descriptor. |
37 |
|
|
|
38 |
root |
1.1 |
Linux::AIO::min_parallel $nthreads |
39 |
|
|
Set the minimum number of AIO threads to $nthreads. The default is |
40 |
|
|
1, which means a single asynchronous operation can be done at one |
41 |
|
|
time (the number of outstanding operations, however, is unlimited). |
42 |
|
|
|
43 |
root |
1.2 |
It is recommended to keep the number of threads low, as some linux |
44 |
root |
1.1 |
kernel versions will scale negatively with the number of threads |
45 |
|
|
(higher parallelity => MUCH higher latency). |
46 |
|
|
|
47 |
root |
1.4 |
Under normal circumstances you don't need to call this function, as |
48 |
|
|
this module automatically starts a single async thread. |
49 |
|
|
|
50 |
root |
1.2 |
Linux::AIO::max_parallel $nthreads |
51 |
|
|
Sets the maximum number of AIO threads to $nthreads. If more than |
52 |
|
|
the specified number of threads are currently running, kill them. |
53 |
|
|
This function blocks until the limit is reached. |
54 |
|
|
|
55 |
|
|
This module automatically runs "max_parallel 0" at program end, to |
56 |
|
|
ensure that all threads are killed and that there are no outstanding |
57 |
|
|
requests. |
58 |
|
|
|
59 |
root |
1.4 |
Under normal circumstances you don't need to call this function. |
60 |
|
|
|
61 |
root |
1.1 |
$fileno = Linux::AIO::poll_fileno |
62 |
|
|
Return the *request result pipe filehandle*. This filehandle must be |
63 |
|
|
polled for reading by some mechanism outside this module (e.g. Event |
64 |
|
|
or select, see below). If the pipe becomes readable you have to call |
65 |
|
|
"poll_cb" to check the results. |
66 |
|
|
|
67 |
root |
1.4 |
See "poll_cb" for an example. |
68 |
|
|
|
69 |
root |
1.1 |
Linux::AIO::poll_cb |
70 |
|
|
Process all outstanding events on the result pipe. You have to call |
71 |
|
|
this regularly. Returns the number of events processed. Returns |
72 |
|
|
immediately when no events are outstanding. |
73 |
|
|
|
74 |
|
|
You can use Event to multiplex, e.g.: |
75 |
|
|
|
76 |
|
|
Event->io (fd => Linux::AIO::poll_fileno, |
77 |
|
|
poll => 'r', async => 1, |
78 |
root |
1.4 |
cb => \&Linux::AIO::poll_cb); |
79 |
root |
1.1 |
|
80 |
root |
1.2 |
Linux::AIO::poll_wait |
81 |
|
|
Wait till the result filehandle becomes ready for reading (simply |
82 |
|
|
does a select on the filehandle. This is useful if you want to |
83 |
|
|
synchronously wait for some requests to finish). |
84 |
|
|
|
85 |
root |
1.4 |
See "nreqs" for an example. |
86 |
|
|
|
87 |
root |
1.1 |
Linux::AIO::nreqs |
88 |
|
|
Returns the number of requests currently outstanding. |
89 |
|
|
|
90 |
root |
1.4 |
Example: wait till there are no outstanding requests anymore: |
91 |
|
|
|
92 |
|
|
Linux::AIO::poll_wait while Linux::AIO::nreqs; |
93 |
|
|
|
94 |
root |
1.1 |
aio_open $pathname, $flags, $mode, $callback |
95 |
|
|
Asynchronously open or create a file and call the callback with the |
96 |
|
|
filedescriptor (NOT a perl filehandle, sorry for that, but watch |
97 |
|
|
out, this might change in the future). |
98 |
|
|
|
99 |
root |
1.4 |
The $mode argument is a bitmask. See the "Fcntl" module for a list. |
100 |
|
|
They are the same as used in "sysopen". |
101 |
|
|
|
102 |
|
|
Example: |
103 |
|
|
|
104 |
|
|
aio_open "/etc/passwd", O_RDONLY, 0, sub { |
105 |
|
|
if ($_[0] >= 0) { |
106 |
|
|
open my $fh, "<&$_[0]"; # create a copy for perl |
107 |
|
|
aio_close $_[0], sub { }; # close the aio handle |
108 |
|
|
print "open successful, fh is $fh\n"; |
109 |
|
|
... |
110 |
|
|
} else { |
111 |
|
|
die "open failed: $!\n"; |
112 |
|
|
} |
113 |
|
|
}; |
114 |
|
|
|
115 |
root |
1.1 |
aio_close $fh, $callback |
116 |
|
|
Asynchronously close a file and call the callback with the result |
117 |
|
|
code. |
118 |
|
|
|
119 |
|
|
aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
120 |
|
|
aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
121 |
|
|
Reads or writes "length" bytes from the specified "fh" and "offset" |
122 |
|
|
into the scalar given by "data" and offset "dataoffset" and calls |
123 |
root |
1.4 |
the callback without the actual number of bytes read (or -1 on |
124 |
|
|
error, just like the syscall). |
125 |
|
|
|
126 |
|
|
Example: Read 15 bytes at offset 7 into scalar $buffer, strating at |
127 |
|
|
offset 0 within the scalar: |
128 |
|
|
|
129 |
|
|
aio_read $fh, 7, 15, $buffer, 0, sub { |
130 |
|
|
$_[0] >= 0 or die "read error: $!"; |
131 |
|
|
print "read <$buffer>\n"; |
132 |
|
|
}; |
133 |
|
|
|
134 |
|
|
aio_readahead $fh,$offset,$length, $callback |
135 |
|
|
Asynchronously reads the specified byte range into the page cache, |
136 |
|
|
using the "readahead" syscall. |
137 |
|
|
|
138 |
|
|
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 |
140 |
|
|
$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 |
142 |
|
|
performed in whole pages, so that offset is effectively rounded down |
143 |
|
|
to a page boundary and bytes are read up to the next page boundary |
144 |
|
|
greater than or equal to (off-set+length). aio_readahead() does not |
145 |
|
|
read beyond the end of the file. The current file offset of the file |
146 |
|
|
is left unchanged. |
147 |
root |
1.1 |
|
148 |
|
|
aio_stat $fh_or_path, $callback |
149 |
|
|
aio_lstat $fh, $callback |
150 |
|
|
Works like perl's "stat" or "lstat" in void context. The callback |
151 |
|
|
will be called after the stat and the results will be available |
152 |
|
|
using "stat _" or "-s _" etc... |
153 |
|
|
|
154 |
|
|
Currently, the stats are always 64-bit-stats, i.e. instead of |
155 |
|
|
returning an error when stat'ing a large file, the results will be |
156 |
|
|
silently truncated unless perl itself is compiled with large file |
157 |
|
|
support. |
158 |
|
|
|
159 |
root |
1.4 |
Example: Print the length of /etc/passwd: |
160 |
|
|
|
161 |
|
|
aio_stat "/etc/passwd", sub { |
162 |
|
|
$_[0] and die "stat failed: $!"; |
163 |
|
|
print "size is ", -s _, "\n"; |
164 |
|
|
}; |
165 |
|
|
|
166 |
root |
1.1 |
aio_unlink $pathname, $callback |
167 |
root |
1.4 |
Asynchronously unlink (delete) a file and call the callback with the |
168 |
|
|
result code. |
169 |
|
|
|
170 |
|
|
aio_fsync $fh, $callback |
171 |
|
|
Asynchronously call fsync on the given filehandle and call the |
172 |
|
|
callback with the fsync result code. |
173 |
|
|
|
174 |
|
|
aio_fdatasync $fh, $callback |
175 |
|
|
Asynchronously call fdatasync on the given filehandle and call the |
176 |
|
|
callback with the fdatasync result code. |
177 |
root |
1.1 |
|
178 |
|
|
BUGS |
179 |
|
|
This module has been extensively tested in a large and very busy |
180 |
|
|
webserver for many years now. |
181 |
|
|
|
182 |
|
|
- aio_open gives a fd, but all other functions expect a perl filehandle. |
183 |
|
|
|
184 |
|
|
SEE ALSO |
185 |
|
|
Coro. |
186 |
|
|
|
187 |
|
|
AUTHOR |
188 |
|
|
Marc Lehmann <schmorp@schmorp.de> |
189 |
|
|
http://home.schmorp.de/ |
190 |
|
|
|