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1.1 |
=head1 NAME |
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IO::AIO - Asynchronous Input/Output |
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=head1 SYNOPSIS |
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use IO::AIO; |
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1.6 |
aio_open "/etc/passwd", O_RDONLY, 0, sub { |
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my ($fh) = @_; |
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... |
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}; |
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aio_unlink "/tmp/file", sub { }; |
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aio_read $fh, 30000, 1024, $buffer, 0, sub { |
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1.8 |
$_[0] > 0 or die "read error: $!"; |
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1.6 |
}; |
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1.42 |
# AnyEvent |
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open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; |
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my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb }); |
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1.6 |
# Event |
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Event->io (fd => IO::AIO::poll_fileno, |
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1.7 |
poll => 'r', |
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1.6 |
cb => \&IO::AIO::poll_cb); |
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# Glib/Gtk2 |
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add_watch Glib::IO IO::AIO::poll_fileno, |
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1.22 |
in => sub { IO::AIO::poll_cb; 1 }; |
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1.6 |
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# Tk |
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Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", |
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readable => \&IO::AIO::poll_cb); |
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1.11 |
# Danga::Socket |
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Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => |
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\&IO::AIO::poll_cb); |
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1.1 |
=head1 DESCRIPTION |
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This module implements asynchronous I/O using whatever means your |
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1.2 |
operating system supports. |
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1.1 |
|
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1.2 |
Currently, a number of threads are started that execute your read/writes |
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and signal their completion. You don't need thread support in your libc or |
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perl, and the threads created by this module will not be visible to the |
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pthreads library. In the future, this module might make use of the native |
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aio functions available on many operating systems. However, they are often |
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not well-supported (Linux doesn't allow them on normal files currently, |
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for example), and they would only support aio_read and aio_write, so the |
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remaining functionality would have to be implemented using threads anyway. |
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1.1 |
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Although the module will work with in the presence of other threads, it is |
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1.22 |
currently not reentrant, so use appropriate locking yourself, always call |
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C<poll_cb> from within the same thread, or never call C<poll_cb> (or other |
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C<aio_> functions) recursively. |
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1.1 |
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=cut |
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package IO::AIO; |
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1.23 |
no warnings; |
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1.1 |
use base 'Exporter'; |
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1.2 |
use Fcntl (); |
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1.1 |
BEGIN { |
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1.49 |
$VERSION = '1.73'; |
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1.1 |
|
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1.39 |
@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat |
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1.40 |
aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink |
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1.38 |
aio_fsync aio_fdatasync aio_readahead); |
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@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel |
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max_outstanding nreqs); |
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1.1 |
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require XSLoader; |
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XSLoader::load IO::AIO, $VERSION; |
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} |
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1.5 |
=head1 FUNCTIONS |
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1.1 |
|
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1.5 |
=head2 AIO FUNCTIONS |
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1.1 |
|
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1.5 |
All the C<aio_*> calls are more or less thin wrappers around the syscall |
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with the same name (sans C<aio_>). The arguments are similar or identical, |
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1.14 |
and they all accept an additional (and optional) C<$callback> argument |
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which must be a code reference. This code reference will get called with |
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the syscall return code (e.g. most syscalls return C<-1> on error, unlike |
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perl, which usually delivers "false") as it's sole argument when the given |
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syscall has been executed asynchronously. |
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1.1 |
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1.23 |
All functions expecting a filehandle keep a copy of the filehandle |
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internally until the request has finished. |
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1.1 |
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1.28 |
The pathnames you pass to these routines I<must> be absolute and |
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encoded in byte form. The reason for the former is that at the time the |
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request is being executed, the current working directory could have |
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changed. Alternatively, you can make sure that you never change the |
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current working directory. |
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To encode pathnames to byte form, either make sure you either: a) |
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always pass in filenames you got from outside (command line, readdir |
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etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode |
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your pathnames to the locale (or other) encoding in effect in the user |
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environment, d) use Glib::filename_from_unicode on unicode filenames or e) |
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use something else. |
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1.1 |
|
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1.5 |
=over 4 |
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1.1 |
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1.40 |
=item aio_open $pathname, $flags, $mode, $callback->($fh) |
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1.1 |
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1.2 |
Asynchronously open or create a file and call the callback with a newly |
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created filehandle for the file. |
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1.1 |
|
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The pathname passed to C<aio_open> must be absolute. See API NOTES, above, |
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for an explanation. |
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1.20 |
The C<$flags> argument is a bitmask. See the C<Fcntl> module for a |
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list. They are the same as used by C<sysopen>. |
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Likewise, C<$mode> specifies the mode of the newly created file, if it |
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didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>, |
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except that it is mandatory (i.e. use C<0> if you don't create new files, |
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and C<0666> or C<0777> if you do). |
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1.1 |
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Example: |
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aio_open "/etc/passwd", O_RDONLY, 0, sub { |
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1.2 |
if ($_[0]) { |
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print "open successful, fh is $_[0]\n"; |
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1.1 |
... |
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} else { |
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die "open failed: $!\n"; |
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} |
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}; |
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1.40 |
=item aio_close $fh, $callback->($status) |
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1.1 |
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1.2 |
Asynchronously close a file and call the callback with the result |
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code. I<WARNING:> although accepted, you should not pass in a perl |
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1.20 |
filehandle here, as perl will likely close the file descriptor another |
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time when the filehandle is destroyed. Normally, you can safely call perls |
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C<close> or just let filehandles go out of scope. |
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This is supposed to be a bug in the API, so that might change. It's |
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therefore best to avoid this function. |
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1.1 |
|
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1.40 |
=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
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1.1 |
|
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1.40 |
=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
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1.1 |
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Reads or writes C<length> bytes from the specified C<fh> and C<offset> |
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into the scalar given by C<data> and offset C<dataoffset> and calls the |
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callback without the actual number of bytes read (or -1 on error, just |
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like the syscall). |
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1.31 |
The C<$data> scalar I<MUST NOT> be modified in any way while the request |
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is outstanding. Modifying it can result in segfaults or WW3 (if the |
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necessary/optional hardware is installed). |
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1.17 |
Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at |
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1.1 |
offset C<0> within the scalar: |
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aio_read $fh, 7, 15, $buffer, 0, sub { |
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1.9 |
$_[0] > 0 or die "read error: $!"; |
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print "read $_[0] bytes: <$buffer>\n"; |
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1.1 |
}; |
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1.40 |
=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) |
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1.35 |
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Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts |
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reading at byte offset C<$in_offset>, and starts writing at the current |
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file offset of C<$out_fh>. Because of that, it is not safe to issue more |
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than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each |
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other. |
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This call tries to make use of a native C<sendfile> syscall to provide |
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zero-copy operation. For this to work, C<$out_fh> should refer to a |
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socket, and C<$in_fh> should refer to mmap'able file. |
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If the native sendfile call fails or is not implemented, it will be |
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1.36 |
emulated, so you can call C<aio_sendfile> on any type of filehandle |
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regardless of the limitations of the operating system. |
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1.35 |
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Please note, however, that C<aio_sendfile> can read more bytes from |
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C<$in_fh> than are written, and there is no way to find out how many |
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1.36 |
bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only |
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provides the number of bytes written to C<$out_fh>. Only if the result |
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value equals C<$length> one can assume that C<$length> bytes have been |
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read. |
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1.35 |
|
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1.40 |
=item aio_readahead $fh,$offset,$length, $callback->($retval) |
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1.1 |
|
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1.20 |
C<aio_readahead> populates the page cache with data from a file so that |
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1.1 |
subsequent reads from that file will not block on disk I/O. The C<$offset> |
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argument specifies the starting point from which data is to be read and |
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C<$length> specifies the number of bytes to be read. I/O is performed in |
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whole pages, so that offset is effectively rounded down to a page boundary |
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and bytes are read up to the next page boundary greater than or equal to |
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1.20 |
(off-set+length). C<aio_readahead> does not read beyond the end of the |
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1.1 |
file. The current file offset of the file is left unchanged. |
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1.26 |
If that syscall doesn't exist (likely if your OS isn't Linux) it will be |
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emulated by simply reading the data, which would have a similar effect. |
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1.40 |
=item aio_stat $fh_or_path, $callback->($status) |
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1.1 |
|
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1.40 |
=item aio_lstat $fh, $callback->($status) |
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1.1 |
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Works like perl's C<stat> or C<lstat> in void context. The callback will |
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be called after the stat and the results will be available using C<stat _> |
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or C<-s _> etc... |
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The pathname passed to C<aio_stat> must be absolute. See API NOTES, above, |
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for an explanation. |
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Currently, the stats are always 64-bit-stats, i.e. instead of returning an |
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error when stat'ing a large file, the results will be silently truncated |
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unless perl itself is compiled with large file support. |
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Example: Print the length of F</etc/passwd>: |
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aio_stat "/etc/passwd", sub { |
228 |
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$_[0] and die "stat failed: $!"; |
229 |
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print "size is ", -s _, "\n"; |
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}; |
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1.40 |
=item aio_unlink $pathname, $callback->($status) |
233 |
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1.1 |
|
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Asynchronously unlink (delete) a file and call the callback with the |
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result code. |
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1.40 |
=item aio_rmdir $pathname, $callback->($status) |
238 |
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1.27 |
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Asynchronously rmdir (delete) a directory and call the callback with the |
240 |
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result code. |
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1.46 |
=item aio_readdir $pathname, $callback->($entries) |
243 |
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1.37 |
|
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Unlike the POSIX call of the same name, C<aio_readdir> reads an entire |
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directory (i.e. opendir + readdir + closedir). The entries will not be |
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sorted, and will B<NOT> include the C<.> and C<..> entries. |
247 |
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248 |
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The callback a single argument which is either C<undef> or an array-ref |
249 |
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with the filenames. |
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1.40 |
=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) |
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Scans a directory (similar to C<aio_readdir>) and tries to separate the |
254 |
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entries of directory C<$path> into two sets of names, ones you can recurse |
255 |
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into (directories), and ones you cannot recurse into (everything else). |
256 |
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C<aio_scandir> is a composite request that consists of many |
258 |
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aio-primitives. C<$maxreq> specifies the maximum number of outstanding |
259 |
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aio requests that this function generates. If it is C<< <= 0 >>, then a |
260 |
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suitable default will be chosen (currently 8). |
261 |
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On error, the callback is called without arguments, otherwise it receives |
263 |
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two array-refs with path-relative entry names. |
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Example: |
266 |
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267 |
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aio_scandir $dir, 0, sub { |
268 |
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my ($dirs, $nondirs) = @_; |
269 |
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print "real directories: @$dirs\n"; |
270 |
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print "everything else: @$nondirs\n"; |
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}; |
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Implementation notes. |
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The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can. |
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After reading the directory, the modification time, size etc. of the |
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directory before and after the readdir is checked, and if they match, the |
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link count will be used to decide how many entries are directories (if |
280 |
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>= 2). Otherwise, no knowledge of the number of subdirectories will be |
281 |
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assumed. |
282 |
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283 |
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Then entires will be sorted into likely directories (everything without a |
284 |
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non-initial dot) and likely non-directories (everything else). Then every |
285 |
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entry + C</.> will be C<stat>'ed, likely directories first. This is often |
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faster because filesystems might detect the type of the entry without |
287 |
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1.48 |
reading the inode data (e.g. ext2fs filetype feature). If that succeeds, |
288 |
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1.40 |
it assumes that the entry is a directory or a symlink to directory (which |
289 |
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will be checked seperately). |
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291 |
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If the known number of directories has been reached, the rest of the |
292 |
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entries is assumed to be non-directories. |
293 |
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294 |
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=cut |
295 |
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296 |
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sub aio_scandir($$$) { |
297 |
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my ($path, $maxreq, $cb) = @_; |
298 |
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299 |
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$maxreq = 8 if $maxreq <= 0; |
300 |
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301 |
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# stat once |
302 |
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aio_stat $path, sub { |
303 |
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1.47 |
return $cb->() if $_[0]; |
304 |
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1.40 |
my $hash1 = join ":", (stat _)[0,1,3,7,9]; |
305 |
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306 |
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# read the directory entries |
307 |
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aio_readdir $path, sub { |
308 |
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my $entries = shift |
309 |
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or return $cb->(); |
310 |
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311 |
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# stat the dir another time |
312 |
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aio_stat $path, sub { |
313 |
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my $hash2 = join ":", (stat _)[0,1,3,7,9]; |
314 |
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315 |
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my $ndirs; |
316 |
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317 |
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# take the slow route if anything looks fishy |
318 |
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if ($hash1 ne $hash2) { |
319 |
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$ndirs = -1; |
320 |
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} else { |
321 |
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# if nlink == 2, we are finished |
322 |
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# on non-posix-fs's, we rely on nlink < 2 |
323 |
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$ndirs = (stat _)[3] - 2 |
324 |
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1.43 |
or return $cb->([], $entries); |
325 |
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1.40 |
} |
326 |
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|
327 |
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# sort into likely dirs and likely nondirs |
328 |
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# dirs == files without ".", short entries first |
329 |
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$entries = [map $_->[0], |
330 |
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sort { $b->[1] cmp $a->[1] } |
331 |
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map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length], |
332 |
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@$entries]; |
333 |
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334 |
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my (@dirs, @nondirs); |
335 |
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336 |
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my ($statcb, $schedcb); |
337 |
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my $nreq = 0; |
338 |
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339 |
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$schedcb = sub { |
340 |
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if (@$entries) { |
341 |
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if ($nreq < $maxreq) { |
342 |
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my $ent = pop @$entries; |
343 |
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$nreq++; |
344 |
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aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) }; |
345 |
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} |
346 |
|
|
} elsif (!$nreq) { |
347 |
|
|
# finished |
348 |
|
|
undef $statcb; |
349 |
|
|
undef $schedcb; |
350 |
root |
1.45 |
$cb->(\@dirs, \@nondirs) if $cb; |
351 |
root |
1.40 |
undef $cb; |
352 |
|
|
} |
353 |
|
|
}; |
354 |
|
|
$statcb = sub { |
355 |
|
|
my ($status, $entry) = @_; |
356 |
|
|
|
357 |
|
|
if ($status < 0) { |
358 |
|
|
$nreq--; |
359 |
|
|
push @nondirs, $entry; |
360 |
|
|
&$schedcb; |
361 |
|
|
} else { |
362 |
|
|
# need to check for real directory |
363 |
|
|
aio_lstat "$path/$entry", sub { |
364 |
|
|
$nreq--; |
365 |
|
|
|
366 |
|
|
if (-d _) { |
367 |
|
|
push @dirs, $entry; |
368 |
|
|
|
369 |
|
|
if (!--$ndirs) { |
370 |
|
|
push @nondirs, @$entries; |
371 |
|
|
$entries = []; |
372 |
|
|
} |
373 |
|
|
} else { |
374 |
|
|
push @nondirs, $entry; |
375 |
|
|
} |
376 |
|
|
|
377 |
|
|
&$schedcb; |
378 |
|
|
} |
379 |
|
|
} |
380 |
|
|
}; |
381 |
|
|
|
382 |
|
|
&$schedcb while @$entries && $nreq < $maxreq; |
383 |
|
|
}; |
384 |
|
|
}; |
385 |
|
|
}; |
386 |
|
|
} |
387 |
|
|
|
388 |
|
|
=item aio_fsync $fh, $callback->($status) |
389 |
root |
1.1 |
|
390 |
|
|
Asynchronously call fsync on the given filehandle and call the callback |
391 |
|
|
with the fsync result code. |
392 |
|
|
|
393 |
root |
1.40 |
=item aio_fdatasync $fh, $callback->($status) |
394 |
root |
1.1 |
|
395 |
|
|
Asynchronously call fdatasync on the given filehandle and call the |
396 |
root |
1.26 |
callback with the fdatasync result code. |
397 |
|
|
|
398 |
|
|
If this call isn't available because your OS lacks it or it couldn't be |
399 |
|
|
detected, it will be emulated by calling C<fsync> instead. |
400 |
root |
1.1 |
|
401 |
root |
1.5 |
=back |
402 |
|
|
|
403 |
|
|
=head2 SUPPORT FUNCTIONS |
404 |
|
|
|
405 |
|
|
=over 4 |
406 |
|
|
|
407 |
|
|
=item $fileno = IO::AIO::poll_fileno |
408 |
|
|
|
409 |
root |
1.20 |
Return the I<request result pipe file descriptor>. This filehandle must be |
410 |
|
|
polled for reading by some mechanism outside this module (e.g. Event or |
411 |
|
|
select, see below or the SYNOPSIS). If the pipe becomes readable you have |
412 |
|
|
to call C<poll_cb> to check the results. |
413 |
root |
1.5 |
|
414 |
|
|
See C<poll_cb> for an example. |
415 |
|
|
|
416 |
|
|
=item IO::AIO::poll_cb |
417 |
|
|
|
418 |
|
|
Process all outstanding events on the result pipe. You have to call this |
419 |
|
|
regularly. Returns the number of events processed. Returns immediately |
420 |
|
|
when no events are outstanding. |
421 |
|
|
|
422 |
root |
1.20 |
Example: Install an Event watcher that automatically calls |
423 |
|
|
IO::AIO::poll_cb with high priority: |
424 |
root |
1.5 |
|
425 |
|
|
Event->io (fd => IO::AIO::poll_fileno, |
426 |
|
|
poll => 'r', async => 1, |
427 |
|
|
cb => \&IO::AIO::poll_cb); |
428 |
|
|
|
429 |
|
|
=item IO::AIO::poll_wait |
430 |
|
|
|
431 |
|
|
Wait till the result filehandle becomes ready for reading (simply does a |
432 |
root |
1.20 |
C<select> on the filehandle. This is useful if you want to synchronously wait |
433 |
root |
1.5 |
for some requests to finish). |
434 |
|
|
|
435 |
|
|
See C<nreqs> for an example. |
436 |
|
|
|
437 |
|
|
=item IO::AIO::nreqs |
438 |
|
|
|
439 |
root |
1.20 |
Returns the number of requests currently outstanding (i.e. for which their |
440 |
|
|
callback has not been invoked yet). |
441 |
root |
1.5 |
|
442 |
|
|
Example: wait till there are no outstanding requests anymore: |
443 |
|
|
|
444 |
|
|
IO::AIO::poll_wait, IO::AIO::poll_cb |
445 |
|
|
while IO::AIO::nreqs; |
446 |
|
|
|
447 |
root |
1.12 |
=item IO::AIO::flush |
448 |
|
|
|
449 |
|
|
Wait till all outstanding AIO requests have been handled. |
450 |
|
|
|
451 |
root |
1.13 |
Strictly equivalent to: |
452 |
|
|
|
453 |
|
|
IO::AIO::poll_wait, IO::AIO::poll_cb |
454 |
|
|
while IO::AIO::nreqs; |
455 |
|
|
|
456 |
|
|
=item IO::AIO::poll |
457 |
|
|
|
458 |
|
|
Waits until some requests have been handled. |
459 |
|
|
|
460 |
|
|
Strictly equivalent to: |
461 |
|
|
|
462 |
|
|
IO::AIO::poll_wait, IO::AIO::poll_cb |
463 |
|
|
if IO::AIO::nreqs; |
464 |
|
|
|
465 |
root |
1.5 |
=item IO::AIO::min_parallel $nthreads |
466 |
|
|
|
467 |
root |
1.34 |
Set the minimum number of AIO threads to C<$nthreads>. The current default |
468 |
|
|
is C<4>, which means four asynchronous operations can be done at one time |
469 |
root |
1.5 |
(the number of outstanding operations, however, is unlimited). |
470 |
|
|
|
471 |
root |
1.34 |
IO::AIO starts threads only on demand, when an AIO request is queued and |
472 |
|
|
no free thread exists. |
473 |
|
|
|
474 |
root |
1.5 |
It is recommended to keep the number of threads low, as some Linux |
475 |
|
|
kernel versions will scale negatively with the number of threads (higher |
476 |
|
|
parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 |
477 |
|
|
threads should be fine. |
478 |
|
|
|
479 |
root |
1.34 |
Under most circumstances you don't need to call this function, as the |
480 |
|
|
module selects a default that is suitable for low to moderate load. |
481 |
root |
1.5 |
|
482 |
|
|
=item IO::AIO::max_parallel $nthreads |
483 |
|
|
|
484 |
root |
1.34 |
Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
485 |
|
|
specified number of threads are currently running, this function kills |
486 |
|
|
them. This function blocks until the limit is reached. |
487 |
|
|
|
488 |
|
|
While C<$nthreads> are zero, aio requests get queued but not executed |
489 |
|
|
until the number of threads has been increased again. |
490 |
root |
1.5 |
|
491 |
|
|
This module automatically runs C<max_parallel 0> at program end, to ensure |
492 |
|
|
that all threads are killed and that there are no outstanding requests. |
493 |
|
|
|
494 |
|
|
Under normal circumstances you don't need to call this function. |
495 |
|
|
|
496 |
|
|
=item $oldnreqs = IO::AIO::max_outstanding $nreqs |
497 |
|
|
|
498 |
|
|
Sets the maximum number of outstanding requests to C<$nreqs>. If you |
499 |
|
|
try to queue up more than this number of requests, the caller will block until |
500 |
|
|
some requests have been handled. |
501 |
|
|
|
502 |
|
|
The default is very large, so normally there is no practical limit. If you |
503 |
root |
1.34 |
queue up many requests in a loop it often improves speed if you set |
504 |
root |
1.5 |
this to a relatively low number, such as C<100>. |
505 |
|
|
|
506 |
|
|
Under normal circumstances you don't need to call this function. |
507 |
|
|
|
508 |
|
|
=back |
509 |
|
|
|
510 |
root |
1.1 |
=cut |
511 |
|
|
|
512 |
root |
1.2 |
# support function to convert a fd into a perl filehandle |
513 |
|
|
sub _fd2fh { |
514 |
|
|
return undef if $_[0] < 0; |
515 |
|
|
|
516 |
root |
1.23 |
# try to generate nice filehandles |
517 |
|
|
my $sym = "IO::AIO::fd#$_[0]"; |
518 |
|
|
local *$sym; |
519 |
root |
1.25 |
|
520 |
root |
1.27 |
open *$sym, "+<&=$_[0]" # usually works under any unix |
521 |
|
|
or open *$sym, "<&=$_[0]" # cygwin needs this |
522 |
|
|
or open *$sym, ">&=$_[0]" # or this |
523 |
root |
1.2 |
or return undef; |
524 |
|
|
|
525 |
root |
1.23 |
*$sym |
526 |
root |
1.2 |
} |
527 |
|
|
|
528 |
root |
1.1 |
min_parallel 4; |
529 |
|
|
|
530 |
|
|
END { |
531 |
|
|
max_parallel 0; |
532 |
|
|
} |
533 |
|
|
|
534 |
|
|
1; |
535 |
|
|
|
536 |
root |
1.27 |
=head2 FORK BEHAVIOUR |
537 |
|
|
|
538 |
root |
1.34 |
Before the fork, IO::AIO enters a quiescent state where no requests |
539 |
|
|
can be added in other threads and no results will be processed. After |
540 |
|
|
the fork the parent simply leaves the quiescent state and continues |
541 |
|
|
request/result processing, while the child clears the request/result |
542 |
|
|
queue (so the requests started before the fork will only be handled in |
543 |
|
|
the parent). Threats will be started on demand until the limit ste in the |
544 |
|
|
parent process has been reached again. |
545 |
root |
1.27 |
|
546 |
root |
1.1 |
=head1 SEE ALSO |
547 |
|
|
|
548 |
|
|
L<Coro>, L<Linux::AIO>. |
549 |
|
|
|
550 |
|
|
=head1 AUTHOR |
551 |
|
|
|
552 |
|
|
Marc Lehmann <schmorp@schmorp.de> |
553 |
|
|
http://home.schmorp.de/ |
554 |
|
|
|
555 |
|
|
=cut |
556 |
|
|
|