Provided by: libio-aio-perl_4.76-1build1_amd64 
NAME
IO::AIO - Asynchronous/Advanced Input/Output
SYNOPSIS
use IO::AIO;
aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
my $fh = shift
or die "/etc/passwd: $!";
...
};
aio_unlink "/tmp/file", sub { };
aio_read $fh, 30000, 1024, $buffer, 0, sub {
$_[0] > 0 or die "read error: $!";
};
# version 2+ has request and group objects
use IO::AIO 2;
aioreq_pri 4; # give next request a very high priority
my $req = aio_unlink "/tmp/file", sub { };
$req->cancel; # cancel request if still in queue
my $grp = aio_group sub { print "all stats done\n" };
add $grp aio_stat "..." for ...;
DESCRIPTION
This module implements asynchronous I/O using whatever means your operating system
supports. It is implemented as an interface to "libeio"
(<http://software.schmorp.de/pkg/libeio.html>).
Asynchronous means that operations that can normally block your program (e.g. reading from
disk) will be done asynchronously: the operation will still block, but you can do
something else in the meantime. This is extremely useful for programs that need to stay
interactive even when doing heavy I/O (GUI programs, high performance network servers
etc.), but can also be used to easily do operations in parallel that are normally done
sequentially, e.g. stat'ing many files, which is much faster on a RAID volume or over NFS
when you do a number of stat operations concurrently.
While most of this works on all types of file descriptors (for example sockets), using
these functions on file descriptors that support nonblocking operation (again, sockets,
pipes etc.) is very inefficient. Use an event loop for that (such as the EV module):
IO::AIO will naturally fit into such an event loop itself.
In this version, a number of threads are started that execute your requests and signal
their completion. You don't need thread support in perl, and the threads created by this
module will not be visible to perl. In the future, this module might make use of the
native aio functions available on many operating systems. However, they are often not
well-supported or restricted (GNU/Linux doesn't allow them on normal files currently, for
example), and they would only support aio_read and aio_write, so the remaining
functionality would have to be implemented using threads anyway.
In addition to asynchronous I/O, this module also exports some rather arcane interfaces,
such as "madvise" or linux's "splice" system call, which is why the "A" in "AIO" can also
mean advanced.
Although the module will work in the presence of other (Perl-) threads, it is currently
not reentrant in any way, so use appropriate locking yourself, always call "poll_cb" from
within the same thread, or never call "poll_cb" (or other "aio_" functions) recursively.
EXAMPLE
This is a simple example that uses the EV module and loads /etc/passwd asynchronously:
use EV;
use IO::AIO;
# register the IO::AIO callback with EV
my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
# queue the request to open /etc/passwd
aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
my $fh = shift
or die "error while opening: $!";
# stat'ing filehandles is generally non-blocking
my $size = -s $fh;
# queue a request to read the file
my $contents;
aio_read $fh, 0, $size, $contents, 0, sub {
$_[0] == $size
or die "short read: $!";
close $fh;
# file contents now in $contents
print $contents;
# exit event loop and program
EV::break;
};
};
# possibly queue up other requests, or open GUI windows,
# check for sockets etc. etc.
# process events as long as there are some:
EV::run;
REQUEST ANATOMY AND LIFETIME
Every "aio_*" function creates a request. which is a C data structure not directly visible
to Perl.
If called in non-void context, every request function returns a Perl object representing
the request. In void context, nothing is returned, which saves a bit of memory.
The perl object is a fairly standard ref-to-hash object. The hash contents are not used by
IO::AIO so you are free to store anything you like in it.
During their existence, aio requests travel through the following states, in order:
ready
Immediately after a request is created it is put into the ready state, waiting for a
thread to execute it.
execute
A thread has accepted the request for processing and is currently executing it (e.g.
blocking in read).
pending
The request has been executed and is waiting for result processing.
While request submission and execution is fully asynchronous, result processing is not
and relies on the perl interpreter calling "poll_cb" (or another function with the
same effect).
result
The request results are processed synchronously by "poll_cb".
The "poll_cb" function will process all outstanding aio requests by calling their
callbacks, freeing memory associated with them and managing any groups they are
contained in.
done
Request has reached the end of its lifetime and holds no resources anymore (except
possibly for the Perl object, but its connection to the actual aio request is severed
and calling its methods will either do nothing or result in a runtime error).
FUNCTIONS
QUICK OVERVIEW
This section simply lists the prototypes most of the functions for quick reference. See
the following sections for function-by-function documentation.
aio_wd $pathname, $callback->($wd)
aio_open $pathname, $flags, $mode, $callback->($fh)
aio_close $fh, $callback->($status)
aio_seek $fh,$offset,$whence, $callback->($offs)
aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
aio_readahead $fh,$offset,$length, $callback->($retval)
aio_stat $fh_or_path, $callback->($status)
aio_lstat $fh, $callback->($status)
aio_statvfs $fh_or_path, $callback->($statvfs)
aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
aio_chown $fh_or_path, $uid, $gid, $callback->($status)
aio_chmod $fh_or_path, $mode, $callback->($status)
aio_truncate $fh_or_path, $offset, $callback->($status)
aio_allocate $fh, $mode, $offset, $len, $callback->($status)
aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
aio_unlink $pathname, $callback->($status)
aio_mknod $pathname, $mode, $dev, $callback->($status)
aio_link $srcpath, $dstpath, $callback->($status)
aio_symlink $srcpath, $dstpath, $callback->($status)
aio_readlink $pathname, $callback->($link)
aio_realpath $pathname, $callback->($path)
aio_rename $srcpath, $dstpath, $callback->($status)
aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
aio_mkdir $pathname, $mode, $callback->($status)
aio_rmdir $pathname, $callback->($status)
aio_readdir $pathname, $callback->($entries)
aio_readdirx $pathname, $flags, $callback->($entries, $flags)
IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
aio_load $pathname, $data, $callback->($status)
aio_copy $srcpath, $dstpath, $callback->($status)
aio_move $srcpath, $dstpath, $callback->($status)
aio_rmtree $pathname, $callback->($status)
aio_fcntl $fh, $cmd, $arg, $callback->($status)
aio_ioctl $fh, $request, $buf, $callback->($status)
aio_sync $callback->($status)
aio_syncfs $fh, $callback->($status)
aio_fsync $fh, $callback->($status)
aio_fdatasync $fh, $callback->($status)
aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
aio_pathsync $pathname, $callback->($status)
aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
aio_mlockall $flags, $callback->($status)
aio_group $callback->(...)
aio_nop $callback->()
$prev_pri = aioreq_pri [$pri]
aioreq_nice $pri_adjust
IO::AIO::poll_wait
IO::AIO::poll_cb
IO::AIO::poll
IO::AIO::flush
IO::AIO::max_poll_reqs $nreqs
IO::AIO::max_poll_time $seconds
IO::AIO::min_parallel $nthreads
IO::AIO::max_parallel $nthreads
IO::AIO::max_idle $nthreads
IO::AIO::idle_timeout $seconds
IO::AIO::max_outstanding $maxreqs
IO::AIO::nreqs
IO::AIO::nready
IO::AIO::npending
IO::AIO::reinit
$nfd = IO::AIO::get_fdlimit
IO::AIO::min_fdlimit $nfd
IO::AIO::sendfile $ofh, $ifh, $offset, $count
IO::AIO::fadvise $fh, $offset, $len, $advice
IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
IO::AIO::munmap $scalar
IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
IO::AIO::madvise $scalar, $offset, $length, $advice
IO::AIO::mprotect $scalar, $offset, $length, $protect
IO::AIO::munlock $scalar, $offset = 0, $length = undef
IO::AIO::munlockall
# stat extensions
$counter = IO::AIO::st_gen
$seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
$nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
$seconds = IO::AIO::st_btimesec
($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
# very much unportable syscalls
IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_len, $flags
IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
IO::AIO::tee $r_fh, $w_fh, $length, $flags
$actual_size = IO::AIO::pipesize $r_fh[, $new_size]
($rfh, $wfh) = IO::AIO::pipe2 [$flags]
$fh = IO::AIO::memfd_create $pathname[, $flags]
$fh = IO::AIO::eventfd [$initval, [$flags]]
$fh = IO::AIO::timerfd_create $clockid[, $flags]
($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
API NOTES
All the "aio_*" calls are more or less thin wrappers around the syscall with the same name
(sans "aio_"). The arguments are similar or identical, and they all accept an additional
(and optional) $callback argument which must be a code reference. This code reference will
be called after the syscall has been executed in an asynchronous fashion. The results of
the request will be passed as arguments to the callback (and, if an error occurred, in $!)
- for most requests the syscall return code (e.g. most syscalls return "-1" on error,
unlike perl, which usually delivers "false").
Some requests (such as "aio_readdir") pass the actual results and communicate failures by
passing "undef".
All functions expecting a filehandle keep a copy of the filehandle internally until the
request has finished.
All functions return request objects of type IO::AIO::REQ that allow further manipulation
of those requests while they are in-flight.
The pathnames you pass to these routines should be absolute. The reason for this is that
at the time the request is being executed, the current working directory could have
changed. Alternatively, you can make sure that you never change the current working
directory anywhere in the program and then use relative paths. You can also take advantage
of IO::AIOs working directory abstraction, that lets you specify paths relative to some
previously-opened "working directory object" - see the description of the "IO::AIO::WD"
class later in this document.
To encode pathnames as octets, either make sure you either: a) always pass in filenames
you got from outside (command line, readdir etc.) without tinkering, b) are in your native
filesystem encoding, c) use the Encode module and encode your pathnames to the locale (or
other) encoding in effect in the user environment, d) use Glib::filename_from_unicode on
unicode filenames or e) use something else to ensure your scalar has the correct contents.
This works, btw. independent of the internal UTF-8 bit, which IO::AIO handles correctly
whether it is set or not.
AIO REQUEST FUNCTIONS
$prev_pri = aioreq_pri [$pri]
Returns the priority value that would be used for the next request and, if $pri is
given, sets the priority for the next aio request.
The default priority is 0, the minimum and maximum priorities are "-4" and 4,
respectively. Requests with higher priority will be serviced first.
The priority will be reset to 0 after each call to one of the "aio_*" functions.
Example: open a file with low priority, then read something from it with higher
priority so the read request is serviced before other low priority open requests
(potentially spamming the cache):
aioreq_pri -3;
aio_open ..., sub {
return unless $_[0];
aioreq_pri -2;
aio_read $_[0], ..., sub {
...
};
};
aioreq_nice $pri_adjust
Similar to "aioreq_pri", but subtracts the given value from the current priority, so
the effect is cumulative.
aio_open $pathname, $flags, $mode, $callback->($fh)
Asynchronously open or create a file and call the callback with a newly created
filehandle for the file (or "undef" in case of an error).
The pathname passed to "aio_open" must be absolute. See API NOTES, above, for an
explanation.
The $flags argument is a bitmask. See the "Fcntl" module for a list. They are the same
as used by "sysopen".
Likewise, $mode specifies the mode of the newly created file, if it didn't exist and
"O_CREAT" has been given, just like perl's "sysopen", except that it is mandatory
(i.e. use 0 if you don't create new files, and 0666 or 0777 if you do). Note that the
$mode will be modified by the umask in effect then the request is being executed, so
better never change the umask.
Example:
aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
if ($_[0]) {
print "open successful, fh is $_[0]\n";
...
} else {
die "open failed: $!\n";
}
};
In addition to all the common open modes/flags ("O_RDONLY", "O_WRONLY", "O_RDWR",
"O_CREAT", "O_TRUNC", "O_EXCL" and "O_APPEND"), the following POSIX and non-POSIX
constants are available (missing ones on your system are, as usual, 0):
"O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY", "O_NOFOLLOW",
"O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY", "O_DSYNC", "O_RSYNC", "O_SYNC",
"O_PATH", "O_TMPFILE", "O_TTY_INIT" and "O_ACCMODE".
aio_close $fh, $callback->($status)
Asynchronously close a file and call the callback with the result code.
Unfortunately, you can't do this to perl. Perl insists very strongly on closing the
file descriptor associated with the filehandle itself.
Therefore, "aio_close" will not close the filehandle - instead it will use dup2 to
overwrite the file descriptor with the write-end of a pipe (the pipe fd will be
created on demand and will be cached).
Or in other words: the file descriptor will be closed, but it will not be free for
reuse until the perl filehandle is closed.
aio_seek $fh, $offset, $whence, $callback->($offs)
Seeks the filehandle to the new $offset, similarly to perl's "sysseek". The $whence
can use the traditional values (0 for "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR"
or 2 for "IO::AIO::SEEK_END").
The resulting absolute offset will be passed to the callback, or "-1" in case of an
error.
In theory, the $whence constants could be different than the corresponding values from
Fcntl, but perl guarantees they are the same, so don't panic.
As a GNU/Linux (and maybe Solaris) extension, also the constants "IO::AIO::SEEK_DATA"
and "IO::AIO::SEEK_HOLE" are available, if they could be found. No guarantees about
suitability for use in "aio_seek" or Perl's "sysseek" can be made though, although I
would naively assume they "just work".
aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
Reads or writes $length bytes from or to the specified $fh and $offset into the scalar
given by $data and offset $dataoffset and calls the callback with the actual number of
bytes transferred (or -1 on error, just like the syscall).
"aio_read" will, like "sysread", shrink or grow the $data scalar to offset plus the
actual number of bytes read.
If $offset is undefined, then the current file descriptor offset will be used (and
updated), otherwise the file descriptor offset will not be changed by these calls.
If $length is undefined in "aio_write", use the remaining length of $data.
If $dataoffset is less than zero, it will be counted from the end of $data.
The $data scalar MUST NOT be modified in any way while the request is outstanding.
Modifying it can result in segfaults or World War III (if the necessary/optional
hardware is installed).
Example: Read 15 bytes at offset 7 into scalar $buffer, starting at offset 0 within
the scalar:
aio_read $fh, 7, 15, $buffer, 0, sub {
$_[0] > 0 or die "read error: $!";
print "read $_[0] bytes: <$buffer>\n";
};
aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
Tries to copy $length bytes from $in_fh to $out_fh. It starts reading at byte offset
$in_offset, and starts writing at the current file offset of $out_fh. Because of that,
it is not safe to issue more than one "aio_sendfile" per $out_fh, as they will
interfere with each other. The same $in_fh works fine though, as this function does
not move or use the file offset of $in_fh.
Please note that "aio_sendfile" can read more bytes from $in_fh than are written, and
there is no way to find out how many more bytes have been read from "aio_sendfile"
alone, as "aio_sendfile" only provides the number of bytes written to $out_fh. Only if
the result value equals $length one can assume that $length bytes have been read.
Unlike with other "aio_" functions, it makes a lot of sense to use "aio_sendfile" on
non-blocking sockets, as long as one end (typically the $in_fh) is a file - the file
I/O will then be asynchronous, while the socket I/O will be non-blocking. Note,
however, that you can run into a trap where "aio_sendfile" reads some data with
readahead, then fails to write all data, and when the socket is ready the next time,
the data in the cache is already lost, forcing "aio_sendfile" to again hit the disk.
Explicit "aio_read" + "aio_write" lets you better control resource usage.
This call tries to make use of a native "sendfile"-like syscall to provide zero-copy
operation. For this to work, $out_fh should refer to a socket, and $in_fh should refer
to an mmap'able file.
If a native sendfile cannot be found or it fails with "ENOSYS", "EINVAL", "ENOTSUP",
"EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK", it will be emulated, so you
can call "aio_sendfile" on any type of filehandle regardless of the limitations of the
operating system.
As native sendfile syscalls (as practically any non-POSIX interface hacked together in
a hurry to improve benchmark numbers) tend to be rather buggy on many systems, this
implementation tries to work around some known bugs in Linux and FreeBSD kernels
(probably others, too), but that might fail, so you really really should check the
return value of "aio_sendfile" - fewer bytes than expected might have been
transferred.
aio_readahead $fh,$offset,$length, $callback->($retval)
"aio_readahead" populates the page cache with data from a file so that subsequent
reads from that file will not block on disk I/O. The $offset argument specifies the
starting point from which data is to be read and $length specifies the number of bytes
to be read. I/O is performed in whole pages, so that offset is effectively rounded
down to a page boundary and bytes are read up to the next page boundary greater than
or equal to (off-set+length). "aio_readahead" does not read beyond the end of the
file. The current file offset of the file is left unchanged.
If that syscall doesn't exist (likely if your kernel isn't Linux) it will be emulated
by simply reading the data, which would have a similar effect.
aio_stat $fh_or_path, $callback->($status)
aio_lstat $fh, $callback->($status)
Works almost exactly like perl's "stat" or "lstat" in void context. The callback will
be called after the stat and the results will be available using "stat _" or "-s _"
and other tests (with the exception of "-B" and "-T").
The pathname passed to "aio_stat" must be absolute. See API NOTES, above, for an
explanation.
Currently, the stats are always 64-bit-stats, i.e. instead of returning an error when
stat'ing a large file, the results will be silently truncated unless perl itself is
compiled with large file support.
To help interpret the mode and dev/rdev stat values, IO::AIO offers the following
constants and functions (if not implemented, the constants will be 0 and the functions
will either "croak" or fall back on traditional behaviour).
"S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG", "S_IFDIR", "S_IFWHT",
"S_IFSOCK", "IO::AIO::major $dev_t", "IO::AIO::minor $dev_t", "IO::AIO::makedev
$major, $minor".
To access higher resolution stat timestamps, see "SUBSECOND STAT TIME ACCESS".
Example: Print the length of /etc/passwd:
aio_stat "/etc/passwd", sub {
$_[0] and die "stat failed: $!";
print "size is ", -s _, "\n";
};
aio_statvfs $fh_or_path, $callback->($statvfs)
Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on whether a file
handle or path was passed.
On success, the callback is passed a hash reference with the following members:
"bsize", "frsize", "blocks", "bfree", "bavail", "files", "ffree", "favail", "fsid",
"flag" and "namemax". On failure, "undef" is passed.
The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY" and "ST_NOSUID".
The following non-POSIX IO::AIO::ST_* flag masks are defined to their correct value
when available, or to 0 on systems that do not support them: "ST_NODEV", "ST_NOEXEC",
"ST_SYNCHRONOUS", "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
"ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
Example: stat "/wd" and dump out the data if successful.
aio_statvfs "/wd", sub {
my $f = $_[0]
or die "statvfs: $!";
use Data::Dumper;
say Dumper $f;
};
# result:
{
bsize => 1024,
bfree => 4333064312,
blocks => 10253828096,
files => 2050765568,
flag => 4096,
favail => 2042092649,
bavail => 4333064312,
ffree => 2042092649,
namemax => 255,
frsize => 1024,
fsid => 1810
}
aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
Works like perl's "utime" function (including the special case of $atime and $mtime
being undef). Fractional times are supported if the underlying syscalls support them.
When called with a pathname, uses utimensat(2) or utimes(2) if available, otherwise
utime(2). If called on a file descriptor, uses futimens(2) or futimes(2) if available,
otherwise returns ENOSYS, so this is not portable.
Examples:
# set atime and mtime to current time (basically touch(1)):
aio_utime "path", undef, undef;
# set atime to current time and mtime to beginning of the epoch:
aio_utime "path", time, undef; # undef==0
aio_chown $fh_or_path, $uid, $gid, $callback->($status)
Works like perl's "chown" function, except that "undef" for either $uid or $gid is
being interpreted as "do not change" (but -1 can also be used).
Examples:
# same as "chown root path" in the shell:
aio_chown "path", 0, -1;
# same as above:
aio_chown "path", 0, undef;
aio_truncate $fh_or_path, $offset, $callback->($status)
Works like truncate(2) or ftruncate(2).
aio_allocate $fh, $mode, $offset, $len, $callback->($status)
Allocates or frees disk space according to the $mode argument. See the linux
"fallocate" documentation for details.
$mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate space, or
"IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file
range.
IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range (without leaving a
hole), "FALLOC_FL_ZERO_RANGE", to zero a range, "FALLOC_FL_INSERT_RANGE" to insert a
range and "FALLOC_FL_UNSHARE_RANGE" to unshare shared blocks (see your fallocate(2)
manpage).
The file system block size used by "fallocate" is presumably the "f_bsize" returned by
"statvfs", but different filesystems and filetypes can dictate other limitations.
If "fallocate" isn't available or cannot be emulated (currently no emulation will be
attempted), passes "-1" and sets $! to "ENOSYS".
aio_chmod $fh_or_path, $mode, $callback->($status)
Works like perl's "chmod" function.
aio_unlink $pathname, $callback->($status)
Asynchronously unlink (delete) a file and call the callback with the result code.
aio_mknod $pathname, $mode, $dev, $callback->($status)
[EXPERIMENTAL]
Asynchronously create a device node (or fifo). See mknod(2).
The only (POSIX-) portable way of calling this function is:
aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
See "aio_stat" for info about some potentially helpful extra constants and functions.
aio_link $srcpath, $dstpath, $callback->($status)
Asynchronously create a new link to the existing object at $srcpath at the path
$dstpath and call the callback with the result code.
aio_symlink $srcpath, $dstpath, $callback->($status)
Asynchronously create a new symbolic link to the existing object at $srcpath at the
path $dstpath and call the callback with the result code.
aio_readlink $pathname, $callback->($link)
Asynchronously read the symlink specified by $path and pass it to the callback. If an
error occurs, nothing or undef gets passed to the callback.
aio_realpath $pathname, $callback->($path)
Asynchronously make the path absolute and resolve any symlinks in $path. The resulting
path only consists of directories (same as Cwd::realpath).
This request can be used to get the absolute path of the current working directory by
passing it a path of . (a single dot).
aio_rename $srcpath, $dstpath, $callback->($status)
Asynchronously rename the object at $srcpath to $dstpath, just as rename(2) and call
the callback with the result code.
On systems that support the AIO::WD working directory abstraction natively, the case
"[$wd, "."]" as $srcpath is specialcased - instead of failing, "rename" is called on
the absolute path of $wd.
aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
Basically a version of "aio_rename" with an additional $flags argument. Calling this
with "$flags=0" is the same as calling "aio_rename".
Non-zero flags are currently only supported on GNU/Linux systems that support
renameat2. Other systems fail with "ENOSYS" in this case.
The following constants are available (missing ones are, as usual 0), see renameat2(2)
for details:
"IO::AIO::RENAME_NOREPLACE", "IO::AIO::RENAME_EXCHANGE" and
"IO::AIO::RENAME_WHITEOUT".
aio_mkdir $pathname, $mode, $callback->($status)
Asynchronously mkdir (create) a directory and call the callback with the result code.
$mode will be modified by the umask at the time the request is executed, so do not
change your umask.
aio_rmdir $pathname, $callback->($status)
Asynchronously rmdir (delete) a directory and call the callback with the result code.
On systems that support the AIO::WD working directory abstraction natively, the case
"[$wd, "."]" is specialcased - instead of failing, "rmdir" is called on the absolute
path of $wd.
aio_readdir $pathname, $callback->($entries)
Unlike the POSIX call of the same name, "aio_readdir" reads an entire directory (i.e.
opendir + readdir + closedir). The entries will not be sorted, and will NOT include
the "." and ".." entries.
The callback is passed a single argument which is either "undef" or an array-ref with
the filenames.
aio_readdirx $pathname, $flags, $callback->($entries, $flags)
Quite similar to "aio_readdir", but the $flags argument allows one to tune behaviour
and output format. In case of an error, $entries will be "undef".
The flags are a combination of the following constants, ORed together (the flags will
also be passed to the callback, possibly modified):
IO::AIO::READDIR_DENTS
Normally the callback gets an arrayref consisting of names only (as with
"aio_readdir"). If this flag is set, then the callback gets an arrayref with
"[$name, $type, $inode]" arrayrefs, each describing a single directory entry in
more detail:
$name is the name of the entry.
$type is one of the "IO::AIO::DT_xxx" constants:
"IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR", "IO::AIO::DT_DIR",
"IO::AIO::DT_BLK", "IO::AIO::DT_REG", "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK",
"IO::AIO::DT_WHT".
"IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If you need to know,
you have to run stat yourself. Also, for speed/memory reasons, the $type scalars
are read-only: you must not modify them.
$inode is the inode number (which might not be exact on systems with 64 bit inode
numbers and 32 bit perls). This field has unspecified content on systems that do
not deliver the inode information.
IO::AIO::READDIR_DIRS_FIRST
When this flag is set, then the names will be returned in an order where likely
directories come first, in optimal stat order. This is useful when you need to
quickly find directories, or you want to find all directories while avoiding to
stat() each entry.
If the system returns type information in readdir, then this is used to find
directories directly. Otherwise, likely directories are names beginning with ".",
or otherwise names with no dots, of which names with short names are tried first.
IO::AIO::READDIR_STAT_ORDER
When this flag is set, then the names will be returned in an order suitable for
stat()'ing each one. That is, when you plan to stat() most or all files in the
given directory, then the returned order will likely be faster.
If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are specified, then the likely
dirs come first, resulting in a less optimal stat order for stat'ing all entries,
but likely a more optimal order for finding subdirectories.
IO::AIO::READDIR_FOUND_UNKNOWN
This flag should not be set when calling "aio_readdirx". Instead, it is being set
by "aio_readdirx", when any of the $type's found were "IO::AIO::DT_UNKNOWN". The
absence of this flag therefore indicates that all $type's are known, which can be
used to speed up some algorithms.
aio_slurp $pathname, $offset, $length, $data, $callback->($status)
Opens, reads and closes the given file. The data is put into $data, which is resized
as required.
If $offset is negative, then it is counted from the end of the file.
If $length is zero, then the remaining length of the file is used. Also, in this case,
the same limitations to modifying $data apply as when IO::AIO::mmap is used, i.e. it
must only be modified in-place with "substr". If the size of the file is known,
specifying a non-zero $length results in a performance advantage.
This request is similar to the older "aio_load" request, but since it is a single
request, it might be more efficient to use.
Example: load /etc/passwd into $passwd.
my $passwd;
aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
$_[0] >= 0
or die "/etc/passwd: $!\n";
printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
print $passwd;
};
IO::AIO::flush;
aio_load $pathname, $data, $callback->($status)
This is a composite request that tries to fully load the given file into memory.
Status is the same as with aio_read.
Using "aio_slurp" might be more efficient, as it is a single request.
aio_copy $srcpath, $dstpath, $callback->($status)
Try to copy the file (directories not supported as either source or destination) from
$srcpath to $dstpath and call the callback with a status of 0 (ok) or "-1" (error, see
$!).
Existing destination files will be truncated.
This is a composite request that creates the destination file with mode 0200 and
copies the contents of the source file into it using "aio_sendfile", followed by
restoring atime, mtime, access mode and uid/gid, in that order.
If an error occurs, the partial destination file will be unlinked, if possible, except
when setting atime, mtime, access mode and uid/gid, where errors are being ignored.
aio_move $srcpath, $dstpath, $callback->($status)
Try to move the file (directories not supported as either source or destination) from
$srcpath to $dstpath and call the callback with a status of 0 (ok) or "-1" (error, see
$!).
This is a composite request that tries to rename(2) the file first; if rename fails
with "EXDEV", it copies the file with "aio_copy" and, if that is successful, unlinks
the $srcpath.
aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
Scans a directory (similar to "aio_readdir") but additionally tries to efficiently
separate the entries of directory $path into two sets of names, directories you can
recurse into (directories), and ones you cannot recurse into (everything else,
including symlinks to directories).
"aio_scandir" is a composite request that generates many sub requests. $maxreq
specifies the maximum number of outstanding aio requests that this function generates.
If it is "<= 0", then a suitable default will be chosen (currently 4).
On error, the callback is called without arguments, otherwise it receives two array-
refs with path-relative entry names.
Example:
aio_scandir $dir, 0, sub {
my ($dirs, $nondirs) = @_;
print "real directories: @$dirs\n";
print "everything else: @$nondirs\n";
};
Implementation notes.
The "aio_readdir" cannot be avoided, but "stat()"'ing every entry can.
If readdir returns file type information, then this is used directly to find
directories.
Otherwise, after reading the directory, the modification time, size etc. of the
directory before and after the readdir is checked, and if they match (and isn't the
current time), the link count will be used to decide how many entries are directories
(if >= 2). Otherwise, no knowledge of the number of subdirectories will be assumed.
Then entries will be sorted into likely directories a non-initial dot currently) and
likely non-directories (see "aio_readdirx"). Then every entry plus an appended "/."
will be "stat"'ed, likely directories first, in order of their inode numbers. If that
succeeds, it assumes that the entry is a directory or a symlink to directory (which
will be checked separately). This is often faster than stat'ing the entry itself
because filesystems might detect the type of the entry without reading the inode data
(e.g. ext2fs filetype feature), even on systems that cannot return the filetype
information on readdir.
If the known number of directories (link count - 2) has been reached, the rest of the
entries is assumed to be non-directories.
This only works with certainty on POSIX (= UNIX) filesystems, which fortunately are
the vast majority of filesystems around.
It will also likely work on non-POSIX filesystems with reduced efficiency as those
tend to return 0 or 1 as link counts, which disables the directory counting heuristic.
aio_rmtree $pathname, $callback->($status)
Delete a directory tree starting (and including) $path, return the status of the final
"rmdir" only. This is a composite request that uses "aio_scandir" to recurse into and
rmdir directories, and unlink everything else.
aio_fcntl $fh, $cmd, $arg, $callback->($status)
aio_ioctl $fh, $request, $buf, $callback->($status)
These work just like the "fcntl" and "ioctl" built-in functions, except they execute
asynchronously and pass the return value to the callback.
Both calls can be used for a lot of things, some of which make more sense to run
asynchronously in their own thread, while some others make less sense. For example,
calls that block waiting for external events, such as locking, will also lock down an
I/O thread while it is waiting, which can deadlock the whole I/O system. At the same
time, there might be no alternative to using a thread to wait.
So in general, you should only use these calls for things that do (filesystem) I/O,
not for things that wait for other events (network, other processes), although if you
are careful and know what you are doing, you still can.
The following constants are available and can be used for normal "ioctl" and "fcntl"
as well (missing ones are, as usual 0):
"F_DUPFD_CLOEXEC",
"F_OFD_GETLK", "F_OFD_SETLK", "F_OFD_GETLKW",
"FIFREEZE", "FITHAW", "FITRIM", "FICLONE", "FICLONERANGE", "FIDEDUPERANGE".
"F_ADD_SEALS", "F_GET_SEALS", "F_SEAL_SEAL", "F_SEAL_SHRINK", "F_SEAL_GROW" and
"F_SEAL_WRITE".
"FS_IOC_GETFLAGS", "FS_IOC_SETFLAGS", "FS_IOC_GETVERSION", "FS_IOC_SETVERSION",
"FS_IOC_FIEMAP".
"FS_IOC_FSGETXATTR", "FS_IOC_FSSETXATTR", "FS_IOC_SET_ENCRYPTION_POLICY",
"FS_IOC_GET_ENCRYPTION_PWSALT", "FS_IOC_GET_ENCRYPTION_POLICY",
"FS_KEY_DESCRIPTOR_SIZE".
"FS_SECRM_FL", "FS_UNRM_FL", "FS_COMPR_FL", "FS_SYNC_FL", "FS_IMMUTABLE_FL",
"FS_APPEND_FL", "FS_NODUMP_FL", "FS_NOATIME_FL", "FS_DIRTY_FL", "FS_COMPRBLK_FL",
"FS_NOCOMP_FL", "FS_ENCRYPT_FL", "FS_BTREE_FL", "FS_INDEX_FL", "FS_JOURNAL_DATA_FL",
"FS_NOTAIL_FL", "FS_DIRSYNC_FL", "FS_TOPDIR_FL", "FS_FL_USER_MODIFIABLE".
"FS_XFLAG_REALTIME", "FS_XFLAG_PREALLOC", "FS_XFLAG_IMMUTABLE", "FS_XFLAG_APPEND",
"FS_XFLAG_SYNC", "FS_XFLAG_NOATIME", "FS_XFLAG_NODUMP", "FS_XFLAG_RTINHERIT",
"FS_XFLAG_PROJINHERIT", "FS_XFLAG_NOSYMLINKS", "FS_XFLAG_EXTSIZE",
"FS_XFLAG_EXTSZINHERIT", "FS_XFLAG_NODEFRAG", "FS_XFLAG_FILESTREAM", "FS_XFLAG_DAX",
"FS_XFLAG_HASATTR",
aio_sync $callback->($status)
Asynchronously call sync and call the callback when finished.
aio_fsync $fh, $callback->($status)
Asynchronously call fsync on the given filehandle and call the callback with the fsync
result code.
aio_fdatasync $fh, $callback->($status)
Asynchronously call fdatasync on the given filehandle and call the callback with the
fdatasync result code.
If this call isn't available because your OS lacks it or it couldn't be detected, it
will be emulated by calling "fsync" instead.
aio_syncfs $fh, $callback->($status)
Asynchronously call the syncfs syscall to sync the filesystem associated to the given
filehandle and call the callback with the syncfs result code. If syncfs is not
available, calls sync(), but returns "-1" and sets errno to "ENOSYS" nevertheless.
aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
Sync the data portion of the file specified by $offset and $length to disk (but NOT
the metadata), by calling the Linux-specific sync_file_range call. If sync_file_range
is not available or it returns ENOSYS, then fdatasync or fsync is being substituted.
$flags can be a combination of "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
"IO::AIO::SYNC_FILE_RANGE_WRITE" and "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to
the sync_file_range manpage for details.
aio_pathsync $pathname, $callback->($status)
This request tries to open, fsync and close the given path. This is a composite
request intended to sync directories after directory operations (E.g. rename). This
might not work on all operating systems or have any specific effect, but usually it
makes sure that directory changes get written to disc. It works for anything that can
be opened for read-only, not just directories.
Future versions of this function might fall back to other methods when "fsync" on the
directory fails (such as calling "sync").
Passes 0 when everything went ok, and "-1" on error.
aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
This is a rather advanced IO::AIO call, which only works on mmap(2)ed scalars (see the
"IO::AIO::mmap" function, although it also works on data scalars managed by the
Sys::Mmap or Mmap modules, note that the scalar must only be modified in-place while
an aio operation is pending on it).
It calls the "msync" function of your OS, if available, with the memory area starting
at $offset in the string and ending $length bytes later. If $length is negative,
counts from the end, and if $length is "undef", then it goes till the end of the
string. The flags can be either "IO::AIO::MS_ASYNC" or "IO::AIO::MS_SYNC", plus an
optional "IO::AIO::MS_INVALIDATE".
aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
This is a rather advanced IO::AIO call, which works best on mmap(2)ed scalars.
It touches (reads or writes) all memory pages in the specified range inside the
scalar. All caveats and parameters are the same as for "aio_msync", above, except for
flags, which must be either 0 (which reads all pages and ensures they are
instantiated) or "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading and
writing an octet from it, which dirties the page).
aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
This is a rather advanced IO::AIO call, which works best on mmap(2)ed scalars.
It reads in all the pages of the underlying storage into memory (if any) and locks
them, so they are not getting swapped/paged out or removed.
If $length is undefined, then the scalar will be locked till the end.
On systems that do not implement "mlock", this function returns "-1" and sets errno to
"ENOSYS".
Note that the corresponding "munlock" is synchronous and is documented under
"MISCELLANEOUS FUNCTIONS".
Example: open a file, mmap and mlock it - both will be undone when $data gets
destroyed.
open my $fh, "<", $path or die "$path: $!";
my $data;
IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
aio_mlock $data; # mlock in background
aio_mlockall $flags, $callback->($status)
Calls the "mlockall" function with the given $flags (a combination of
"IO::AIO::MCL_CURRENT", "IO::AIO::MCL_FUTURE" and "IO::AIO::MCL_ONFAULT").
On systems that do not implement "mlockall", this function returns "-1" and sets errno
to "ENOSYS". Similarly, flag combinations not supported by the system result in a
return value of "-1" with errno being set to "EINVAL".
Note that the corresponding "munlockall" is synchronous and is documented under
"MISCELLANEOUS FUNCTIONS".
Example: asynchronously lock all current and future pages into memory.
aio_mlockall IO::AIO::MCL_FUTURE;
aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
Queries the extents of the given file (by calling the Linux "FIEMAP" ioctl, see
<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If the ioctl is not
available on your OS, then this request will fail with "ENOSYS".
$start is the starting offset to query extents for, $length is the size of the range
to query - if it is "undef", then the whole file will be queried.
$flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
"IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is also exported), and
is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to query the data portion.
$count is the maximum number of extent records to return. If it is "undef", then
IO::AIO queries all extents of the range. As a very special case, if it is 0, then the
callback receives the number of extents instead of the extents themselves (which is
unreliable, see below).
If an error occurs, the callback receives no arguments. The special "errno" value
"IO::AIO::EBADR" is available to test for flag errors.
Otherwise, the callback receives an array reference with extent structures. Each
extent structure is an array reference itself, with the following members:
[$logical, $physical, $length, $flags]
Flags is any combination of the following flag values (typically either 0 or
"IO::AIO::FIEMAP_EXTENT_LAST" (1)):
"IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
"IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
"IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED", "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
"IO::AIO::FIEMAP_EXTENT_DATA_INLINE", "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
"IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED" or
"IO::AIO::FIEMAP_EXTENT_SHARED".
At the time of this writing (Linux 3.2), this request is unreliable unless $count is
"undef", as the kernel has all sorts of bugs preventing it to return all extents of a
range for files with a large number of extents. The code (only) works around all these
issues if $count is "undef".
aio_group $callback->(...)
This is a very special aio request: Instead of doing something, it is a container for
other aio requests, which is useful if you want to bundle many requests into a single,
composite, request with a definite callback and the ability to cancel the whole
request with its subrequests.
Returns an object of class IO::AIO::GRP. See its documentation below for more info.
Example:
my $grp = aio_group sub {
print "all stats done\n";
};
add $grp
(aio_stat ...),
(aio_stat ...),
...;
aio_nop $callback->()
This is a special request - it does nothing in itself and is only used for side
effects, such as when you want to add a dummy request to a group so that finishing the
requests in the group depends on executing the given code.
While this request does nothing, it still goes through the execution phase and still
requires a worker thread. Thus, the callback will not be executed immediately but only
after other requests in the queue have entered their execution phase. This can be used
to measure request latency.
IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
Mainly used for debugging and benchmarking, this aio request puts one of the request
workers to sleep for the given time.
While it is theoretically handy to have simple I/O scheduling requests like sleep and
file handle readable/writable, the overhead this creates is immense (it blocks a
thread for a long time) so do not use this function except to put your application
under artificial I/O pressure.
IO::AIO::WD - multiple working directories
Your process only has one current working directory, which is used by all threads. This
makes it hard to use relative paths (some other component could call "chdir" at any time,
and it is hard to control when the path will be used by IO::AIO).
One solution for this is to always use absolute paths. This usually works, but can be
quite slow (the kernel has to walk the whole path on every access), and can also be a
hassle to implement.
Newer POSIX systems have a number of functions (openat, fdopendir, futimensat and so on)
that make it possible to specify working directories per operation.
For portability, and because the clowns who "designed", or shall I write, perpetrated this
new interface were obviously half-drunk, this abstraction cannot be perfect, though.
IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD object. This
object stores the canonicalised, absolute version of the path, and on systems that allow
it, also a directory file descriptor.
Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat" or "aio_unlink"),
one can specify an array reference with an IO::AIO::WD object and a pathname instead (or
the IO::AIO::WD object alone, which gets interpreted as "[$wd, "."]"). If the pathname is
absolute, the IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
to that IO::AIO::WD object.
For example, to get a wd object for /etc and then stat passwd inside, you would write:
aio_wd "/etc", sub {
my $etcdir = shift;
# although $etcdir can be undef on error, there is generally no reason
# to check for errors here, as aio_stat will fail with ENOENT
# when $etcdir is undef.
aio_stat [$etcdir, "passwd"], sub {
# yay
};
};
The fact that "aio_wd" is a request and not a normal function shows that creating an
IO::AIO::WD object is itself a potentially blocking operation, which is why it is done
asynchronously.
To stat the directory obtained with "aio_wd" above, one could write either of the
following three request calls:
aio_lstat "/etc" , sub { ... # pathname as normal string
aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
aio_lstat $wd , sub { ... # shorthand for the previous
As with normal pathnames, IO::AIO keeps a copy of the working directory object and the
pathname string, so you could write the following without causing any issues due to $path
getting reused:
my $path = [$wd, undef];
for my $name (qw(abc def ghi)) {
$path->[1] = $name;
aio_stat $path, sub {
# ...
};
}
There are some caveats: when directories get renamed (or deleted), the pathname string
doesn't change, so will point to the new directory (or nowhere at all), while the
directory fd, if available on the system, will still point to the original directory. Most
functions accepting a pathname will use the directory fd on newer systems, and the string
on older systems. Some functions (such as "aio_realpath") will always rely on the string
form of the pathname.
So this functionality is mainly useful to get some protection against "chdir", to easily
get an absolute path out of a relative path for future reference, and to speed up doing
many operations in the same directory (e.g. when stat'ing all files in a directory).
The following functions implement this working directory abstraction:
aio_wd $pathname, $callback->($wd)
Asynchronously canonicalise the given pathname and convert it to an IO::AIO::WD object
representing it. If possible and supported on the system, also open a directory fd to
speed up pathname resolution relative to this working directory.
If something goes wrong, then "undef" is passwd to the callback instead of a working
directory object and $! is set appropriately. Since passing "undef" as working
directory component of a pathname fails the request with "ENOENT", there is often no
need for error checking in the "aio_wd" callback, as future requests using the value
will fail in the expected way.
IO::AIO::CWD
This is a compile time constant (object) that represents the process current working
directory.
Specifying this object as working directory object for a pathname is as if the
pathname would be specified directly, without a directory object. For example, these
calls are functionally identical:
aio_stat "somefile", sub { ... };
aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
To recover the path associated with an IO::AIO::WD object, you can use "aio_realpath":
aio_realpath $wd, sub {
warn "path is $_[0]\n";
};
Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir" sometimes, fall back to
using an absolue path.
IO::AIO::REQ CLASS
All non-aggregate "aio_*" functions return an object of this class when called in non-void
context.
cancel $req
Cancels the request, if possible. Has the effect of skipping execution when entering
the execute state and skipping calling the callback when entering the the result
state, but will leave the request otherwise untouched (with the exception of readdir).
That means that requests that currently execute will not be stopped and resources held
by the request will not be freed prematurely.
cb $req $callback->(...)
Replace (or simply set) the callback registered to the request.
IO::AIO::GRP CLASS
This class is a subclass of IO::AIO::REQ, so all its methods apply to objects of this
class, too.
A IO::AIO::GRP object is a special request that can contain multiple other aio requests.
You create one by calling the "aio_group" constructing function with a callback that will
be called when all contained requests have entered the "done" state:
my $grp = aio_group sub {
print "all requests are done\n";
};
You add requests by calling the "add" method with one or more "IO::AIO::REQ" objects:
$grp->add (aio_unlink "...");
add $grp aio_stat "...", sub {
$_[0] or return $grp->result ("error");
# add another request dynamically, if first succeeded
add $grp aio_open "...", sub {
$grp->result ("ok");
};
};
This makes it very easy to create composite requests (see the source of "aio_move" for an
application) that work and feel like simple requests.
• The IO::AIO::GRP objects will be cleaned up during calls to "IO::AIO::poll_cb", just
like any other request.
• They can be canceled like any other request. Canceling will cancel not only the
request itself, but also all requests it contains.
• They can also can also be added to other IO::AIO::GRP objects.
• You must not add requests to a group from within the group callback (or any later
time).
Their lifetime, simplified, looks like this: when they are empty, they will finish very
quickly. If they contain only requests that are in the "done" state, they will also
finish. Otherwise they will continue to exist.
That means after creating a group you have some time to add requests (precisely before the
callback has been invoked, which is only done within the "poll_cb"). And in the callbacks
of those requests, you can add further requests to the group. And only when all those
requests have finished will the the group itself finish.
add $grp ...
$grp->add (...)
Add one or more requests to the group. Any type of IO::AIO::REQ can be added,
including other groups, as long as you do not create circular dependencies.
Returns all its arguments.
$grp->cancel_subs
Cancel all subrequests and clears any feeder, but not the group request itself. Useful
when you queued a lot of events but got a result early.
The group request will finish normally (you cannot add requests to the group).
$grp->result (...)
Set the result value(s) that will be passed to the group callback when all subrequests
have finished and set the groups errno to the current value of errno (just like
calling "errno" without an error number). By default, no argument will be passed and
errno is zero.
$grp->errno ([$errno])
Sets the group errno value to $errno, or the current value of errno when the argument
is missing.
Every aio request has an associated errno value that is restored when the callback is
invoked. This method lets you change this value from its default (0).
Calling "result" will also set errno, so make sure you either set $! before the call
to "result", or call c<errno> after it.
feed $grp $callback->($grp)
Sets a feeder/generator on this group: every group can have an attached generator that
generates requests if idle. The idea behind this is that, although you could just
queue as many requests as you want in a group, this might starve other requests for a
potentially long time. For example, "aio_scandir" might generate hundreds of thousands
of "aio_stat" requests, delaying any later requests for a long time.
To avoid this, and allow incremental generation of requests, you can instead a group
and set a feeder on it that generates those requests. The feed callback will be called
whenever there are few enough (see "limit", below) requests active in the group itself
and is expected to queue more requests.
The feed callback can queue as many requests as it likes (i.e. "add" does not impose
any limits).
If the feed does not queue more requests when called, it will be automatically removed
from the group.
If the feed limit is 0 when this method is called, it will be set to 2 automatically.
Example:
# stat all files in @files, but only ever use four aio requests concurrently:
my $grp = aio_group sub { print "finished\n" };
limit $grp 4;
feed $grp sub {
my $file = pop @files
or return;
add $grp aio_stat $file, sub { ... };
};
limit $grp $num
Sets the feeder limit for the group: The feeder will be called whenever the group
contains less than this many requests.
Setting the limit to 0 will pause the feeding process.
The default value for the limit is 0, but note that setting a feeder automatically
bumps it up to 2.
SUPPORT FUNCTIONS
EVENT PROCESSING AND EVENT LOOP INTEGRATION
$fileno = IO::AIO::poll_fileno
Return the request result pipe file descriptor. This filehandle must be polled for
reading by some mechanism outside this module (e.g. EV, Glib, select and so on, see
below or the SYNOPSIS). If the pipe becomes readable you have to call "poll_cb" to
check the results.
See "poll_cb" for an example.
IO::AIO::poll_cb
Process some requests that have reached the result phase (i.e. they have been executed
but the results are not yet reported). You have to call this "regularly" to finish
outstanding requests.
Returns 0 if all events could be processed (or there were no events to process), or
"-1" if it returned earlier for whatever reason. Returns immediately when no events
are outstanding. The amount of events processed depends on the settings of
"IO::AIO::max_poll_req", "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
If not all requests were processed for whatever reason, the poll file descriptor will
still be ready when "poll_cb" returns, so normally you don't have to do anything
special to have it called later.
Apart from calling "IO::AIO::poll_cb" when the event filehandle becomes ready, it can
be beneficial to call this function from loops which submit a lot of requests, to make
sure the results get processed when they become available and not just when the loop
is finished and the event loop takes over again. This function returns very fast when
there are no outstanding requests.
Example: Install an Event watcher that automatically calls IO::AIO::poll_cb with high
priority (more examples can be found in the SYNOPSIS section, at the top of this
document):
Event->io (fd => IO::AIO::poll_fileno,
poll => 'r', async => 1,
cb => \&IO::AIO::poll_cb);
IO::AIO::poll_wait
Wait until either at least one request is in the result phase or no requests are
outstanding anymore.
This is useful if you want to synchronously wait for some requests to become ready,
without actually handling them.
See "nreqs" for an example.
IO::AIO::poll
Waits until some requests have been handled.
Returns the number of requests processed, but is otherwise strictly equivalent to:
IO::AIO::poll_wait, IO::AIO::poll_cb
IO::AIO::flush
Wait till all outstanding AIO requests have been handled.
Strictly equivalent to:
IO::AIO::poll_wait, IO::AIO::poll_cb
while IO::AIO::nreqs;
This function can be useful at program aborts, to make sure outstanding I/O has been
done ("IO::AIO" uses an "END" block which already calls this function on normal
exits), or when you are merely using "IO::AIO" for its more advanced functions, rather
than for async I/O, e.g.:
my ($dirs, $nondirs);
IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
IO::AIO::flush;
# $dirs, $nondirs are now set
IO::AIO::max_poll_reqs $nreqs
IO::AIO::max_poll_time $seconds
These set the maximum number of requests (default 0, meaning infinity) that are being
processed by "IO::AIO::poll_cb" in one call, respectively the maximum amount of time
(default 0, meaning infinity) spent in "IO::AIO::poll_cb" to process requests (more
correctly the minimum amount of time "poll_cb" is allowed to use).
Setting "max_poll_time" to a non-zero value creates an overhead of one syscall per
request processed, which is not normally a problem unless your callbacks are really
really fast or your OS is really really slow (I am not mentioning Solaris here). Using
"max_poll_reqs" incurs no overhead.
Setting these is useful if you want to ensure some level of interactiveness when perl
is not fast enough to process all requests in time.
For interactive programs, values such as 0.01 to 0.1 should be fine.
Example: Install an Event watcher that automatically calls IO::AIO::poll_cb with low
priority, to ensure that other parts of the program get the CPU sometimes even under
high AIO load.
# try not to spend much more than 0.1s in poll_cb
IO::AIO::max_poll_time 0.1;
# use a low priority so other tasks have priority
Event->io (fd => IO::AIO::poll_fileno,
poll => 'r', nice => 1,
cb => &IO::AIO::poll_cb);
CONTROLLING THE NUMBER OF THREADS
IO::AIO::min_parallel $nthreads
Set the minimum number of AIO threads to $nthreads. The current default is 8, which
means eight asynchronous operations can execute concurrently at any one time (the
number of outstanding requests, however, is unlimited).
IO::AIO starts threads only on demand, when an AIO request is queued and no free
thread exists. Please note that queueing up a hundred requests can create demand for a
hundred threads, even if it turns out that everything is in the cache and could have
been processed faster by a single thread.
It is recommended to keep the number of threads relatively low, as some Linux kernel
versions will scale negatively with the number of threads (higher parallelity => MUCH
higher latency). With current Linux 2.6 versions, 4-32 threads should be fine.
Under most circumstances you don't need to call this function, as the module selects a
default that is suitable for low to moderate load.
IO::AIO::max_parallel $nthreads
Sets the maximum number of AIO threads to $nthreads. If more than the specified number
of threads are currently running, this function kills them. This function blocks until
the limit is reached.
While $nthreads are zero, aio requests get queued but not executed until the number of
threads has been increased again.
This module automatically runs "max_parallel 0" at program end, to ensure that all
threads are killed and that there are no outstanding requests.
Under normal circumstances you don't need to call this function.
IO::AIO::max_idle $nthreads
Limit the number of threads (default: 4) that are allowed to idle (i.e., threads that
did not get a request to process within the idle timeout (default: 10 seconds). That
means if a thread becomes idle while $nthreads other threads are also idle, it will
free its resources and exit.
This is useful when you allow a large number of threads (e.g. 100 or 1000) to allow
for extremely high load situations, but want to free resources under normal
circumstances (1000 threads can easily consume 30MB of RAM).
The default is probably ok in most situations, especially if thread creation is fast.
If thread creation is very slow on your system you might want to use larger values.
IO::AIO::idle_timeout $seconds
Sets the minimum idle timeout (default 10) after which worker threads are allowed to
exit. SEe "IO::AIO::max_idle".
IO::AIO::max_outstanding $maxreqs
Sets the maximum number of outstanding requests to $nreqs. If you do queue up more
than this number of requests, the next call to "IO::AIO::poll_cb" (and other functions
calling "poll_cb", such as "IO::AIO::flush" or "IO::AIO::poll") will block until the
limit is no longer exceeded.
In other words, this setting does not enforce a queue limit, but can be used to make
poll functions block if the limit is exceeded.
This is a very bad function to use in interactive programs because it blocks, and a
bad way to reduce concurrency because it is inexact: Better use an "aio_group"
together with a feed callback.
Its main use is in scripts without an event loop - when you want to stat a lot of
files, you can write something like this:
IO::AIO::max_outstanding 32;
for my $path (...) {
aio_stat $path , ...;
IO::AIO::poll_cb;
}
IO::AIO::flush;
The call to "poll_cb" inside the loop will normally return instantly, but as soon as
more thna 32 requests are in-flight, it will block until some requests have been
handled. This keeps the loop from pushing a large number of "aio_stat" requests onto
the queue.
The default value for "max_outstanding" is very large, so there is no practical limit
on the number of outstanding requests.
STATISTICAL INFORMATION
IO::AIO::nreqs
Returns the number of requests currently in the ready, execute or pending states (i.e.
for which their callback has not been invoked yet).
Example: wait till there are no outstanding requests anymore:
IO::AIO::poll_wait, IO::AIO::poll_cb
while IO::AIO::nreqs;
IO::AIO::nready
Returns the number of requests currently in the ready state (not yet executed).
IO::AIO::npending
Returns the number of requests currently in the pending state (executed, but not yet
processed by poll_cb).
SUBSECOND STAT TIME ACCESS
Both "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" functions can generally find
access/modification and change times with subsecond time accuracy of the system supports
it, but perl's built-in functions only return the integer part.
The following functions return the timestamps of the most recent stat with subsecond
precision on most systems and work both after "aio_stat"/"aio_lstat" and perl's
"stat"/"lstat" calls. Their return value is only meaningful after a successful
"stat"/"lstat" call, or during/after a successful "aio_stat"/"aio_lstat" callback.
This is similar to the Time::HiRes "stat" functions, but can return full resolution
without rounding and work with standard perl "stat", alleviating the need to call the
special "Time::HiRes" functions, which do not act like their perl counterparts.
On operating systems or file systems where subsecond time resolution is not supported or
could not be detected, a fractional part of 0 is returned, so it is always safe to call
these functions.
$seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
Return the access, modication, change or birth time, respectively, including
fractional part. Due to the limited precision of floating point, the accuracy on most
platforms is only a bit better than milliseconds for times around now - see the nsec
function family, below, for full accuracy.
File birth time is only available when the OS and perl support it (on FreeBSD and
NetBSD at the time of this writing, although support is adaptive, so if your OS/perl
gains support, IO::AIO can take advantage of it). On systems where it isn't available,
0 is currently returned, but this might change to "undef" in a future version.
($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
Returns access, modification, change and birth time all in one go, and maybe more
times in the future version.
$nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec,
IO::AIO::st_btimensec
Return the fractional access, modification, change or birth time, in nanoseconds, as
an integer in the range 0 to 999999999.
Note that no accessors are provided for access, modification and change times - you
need to get those from "stat _" if required ("int IO::AIO::st_atime" and so on will
not generally give you the correct value).
$seconds = IO::AIO::st_btimesec
The (integral) seconds part of the file birth time, if available.
($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
Like the functions above, but returns all four times in one go (and maybe more in
future versions).
$counter = IO::AIO::st_gen
Returns the generation counter (in practice this is just a random number) of the file.
This is only available on platforms which have this member in their "struct stat"
(most BSDs at the time of this writing) and generally only to the root usert. If
unsupported, 0 is returned, but this might change to "undef" in a future version.
Example: print the high resolution modification time of /etc, using "stat", and
"IO::AIO::aio_stat".
if (stat "/etc") {
printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
}
IO::AIO::aio_stat "/etc", sub {
$_[0]
and return;
printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
};
IO::AIO::flush;
Output of the awbove on my system, showing reduced and full accuracy:
stat(/etc) mtime: 1534043702.020808
aio_stat(/etc) mtime: 1534043702.020807792
MISCELLANEOUS FUNCTIONS
IO::AIO implements some functions that are useful when you want to use some "Advanced I/O"
function not available to in Perl, without going the "Asynchronous I/O" route. Many of
these have an asynchronous "aio_*" counterpart.
$numfd = IO::AIO::get_fdlimit
Tries to find the current file descriptor limit and returns it, or "undef" and sets $!
in case of an error. The limit is one larger than the highest valid file descriptor
number.
IO::AIO::min_fdlimit [$numfd]
Try to increase the current file descriptor limit(s) to at least $numfd by changing
the soft or hard file descriptor resource limit. If $numfd is missing, it will try to
set a very high limit, although this is not recommended when you know the actual
minimum that you require.
If the limit cannot be raised enough, the function makes a best-effort attempt to
increase the limit as much as possible, using various tricks, while still failing. You
can query the resulting limit using "IO::AIO::get_fdlimit".
If an error occurs, returns "undef" and sets $!, otherwise returns true.
IO::AIO::sendfile $ofh, $ifh, $offset, $count
Calls the "eio_sendfile_sync" function, which is like "aio_sendfile", but is blocking
(this makes most sense if you know the input data is likely cached already and the
output filehandle is set to non-blocking operations).
Returns the number of bytes copied, or "-1" on error.
IO::AIO::fadvise $fh, $offset, $len, $advice
Simply calls the "posix_fadvise" function (see its manpage for details). The following
advice constants are available: "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE", "IO::AIO::FADV_WILLNEED",
"IO::AIO::FADV_DONTNEED".
On systems that do not implement "posix_fadvise", this function returns ENOSYS,
otherwise the return value of "posix_fadvise".
IO::AIO::madvise $scalar, $offset, $len, $advice
Simply calls the "posix_madvise" function (see its manpage for details). The following
advice constants are available: "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
"IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED", "IO::AIO::MADV_DONTNEED".
If $offset is negative, counts from the end. If $length is negative, the remaining
length of the $scalar is used. If possible, $length will be reduced to fit into the
$scalar.
On systems that do not implement "posix_madvise", this function returns ENOSYS,
otherwise the return value of "posix_madvise".
IO::AIO::mprotect $scalar, $offset, $len, $protect
Simply calls the "mprotect" function on the preferably AIO::mmap'ed $scalar (see its
manpage for details). The following protect constants are available:
"IO::AIO::PROT_NONE", "IO::AIO::PROT_READ", "IO::AIO::PROT_WRITE",
"IO::AIO::PROT_EXEC".
If $offset is negative, counts from the end. If $length is negative, the remaining
length of the $scalar is used. If possible, $length will be reduced to fit into the
$scalar.
On systems that do not implement "mprotect", this function returns ENOSYS, otherwise
the return value of "mprotect".
IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
Memory-maps a file (or anonymous memory range) and attaches it to the given $scalar,
which will act like a string scalar. Returns true on success, and false otherwise.
The scalar must exist, but its contents do not matter - this means you cannot use a
nonexistent array or hash element. When in doubt, "undef" the scalar first.
The only operations allowed on the mmapped scalar are "substr"/"vec", which don't
change the string length, and most read-only operations such as copying it or
searching it with regexes and so on.
Anything else is unsafe and will, at best, result in memory leaks.
The memory map associated with the $scalar is automatically removed when the $scalar
is undef'd or destroyed, or when the "IO::AIO::mmap" or "IO::AIO::munmap" functions
are called on it.
This calls the "mmap"(2) function internally. See your system's manual page for
details on the $length, $prot and $flags parameters.
The $length must be larger than zero and smaller than the actual filesize.
$prot is a combination of "IO::AIO::PROT_NONE", "IO::AIO::PROT_EXEC",
"IO::AIO::PROT_READ" and/or "IO::AIO::PROT_WRITE",
$flags can be a combination of "IO::AIO::MAP_SHARED" or "IO::AIO::MAP_PRIVATE", or a
number of system-specific flags (when not available, the are 0):
"IO::AIO::MAP_ANONYMOUS" (which is set to "MAP_ANON" if your system only provides this
constant), "IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE",
"IO::AIO::MAP_NONBLOCK", "IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
"IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_STACK",
"IO::AIO::MAP_FIXED_NOREPLACE", "IO::AIO::MAP_SHARED_VALIDATE", "IO::AIO::MAP_SYNC" or
"IO::AIO::MAP_UNINITIALIZED".
If $fh is "undef", then a file descriptor of "-1" is passed.
$offset is the offset from the start of the file - it generally must be a multiple of
"IO::AIO::PAGESIZE" and defaults to 0.
Example:
use Digest::MD5;
use IO::AIO;
open my $fh, "<verybigfile"
or die "$!";
IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
or die "verybigfile: $!";
my $fast_md5 = md5 $data;
IO::AIO::munmap $scalar
Removes a previous mmap and undefines the $scalar.
IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
Calls the Linux-specific mremap(2) system call. The $scalar must have been mapped by
"IO::AIO::mmap", and $flags must currently either be 0 or "IO::AIO::MREMAP_MAYMOVE".
Returns true if successful, and false otherwise. If the underlying mmapped region has
changed address, then the true value has the numerical value 1, otherwise it has the
numerical value 0:
my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
or die "mremap: $!";
if ($success*1) {
warn "scalar has chanegd address in memory\n";
}
"IO::AIO::MREMAP_FIXED" and the $new_address argument are currently implemented, but
not supported and might go away in a future version.
On systems where this call is not supported or is not emulated, this call returns
falls and sets $! to "ENOSYS".
IO::AIO::mlockall $flags
Calls the "eio_mlockall_sync" function, which is like "aio_mlockall", but is blocking.
IO::AIO::munlock $scalar, $offset = 0, $length = undef
Calls the "munlock" function, undoing the effects of a previous "aio_mlock" call (see
its description for details).
IO::AIO::munlockall
Calls the "munlockall" function.
On systems that do not implement "munlockall", this function returns ENOSYS, otherwise
the return value of "munlockall".
$fh = IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_maxlen, $flags
Uses the GNU/Linux accept4(2) syscall, if available, to accept a socket and return the
new file handle on success, or sets $! and returns "undef" on error.
The remote name of the new socket will be stored in $sockaddr, which will be extended
to allow for at least $sockaddr_maxlen octets. If the socket name does not fit into
$sockaddr_maxlen octets, this is signaled by returning a longer string in $sockaddr,
which might or might not be truncated.
To accept name-less sockets, use "undef" for $sockaddr and 0 for $sockaddr_maxlen.
The main reasons to use this syscall rather than portable accept(2) are that you can
specify "SOCK_NONBLOCK" and/or "SOCK_CLOEXEC" flags and you can accept name-less
sockets by specifying 0 for $sockaddr_maxlen, which is sadly not possible with perl's
interface to "accept".
IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
Calls the GNU/Linux splice(2) syscall, if available. If $r_off or $w_off are "undef",
then "NULL" is passed for these, otherwise they should be the file offset.
$r_fh and $w_fh should not refer to the same file, as splice might silently corrupt
the data in this case.
The following symbol flag values are available: "IO::AIO::SPLICE_F_MOVE",
"IO::AIO::SPLICE_F_NONBLOCK", "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
See the splice(2) manpage for details.
IO::AIO::tee $r_fh, $w_fh, $length, $flags
Calls the GNU/Linux tee(2) syscall, see its manpage and the description for
"IO::AIO::splice" above for details.
$actual_size = IO::AIO::pipesize $r_fh[, $new_size]
Attempts to query or change the pipe buffer size. Obviously works only on pipes, and
currently works only on GNU/Linux systems, and fails with "-1"/"ENOSYS" everywhere
else. If anybody knows how to influence pipe buffer size on other systems, drop me a
note.
($rfh, $wfh) = IO::AIO::pipe2 [$flags]
This is a direct interface to the Linux pipe2(2) system call. If $flags is missing or
0, then this should be the same as a call to perl's built-in "pipe" function and
create a new pipe, and works on systems that lack the pipe2 syscall. On win32, this
case invokes "_pipe (..., 4096, O_BINARY)".
If $flags is non-zero, it tries to invoke the pipe2 system call with the given flags
(Linux 2.6.27, glibc 2.9).
On success, the read and write file handles are returned.
On error, nothing will be returned. If the pipe2 syscall is missing and $flags is non-
zero, fails with "ENOSYS".
Please refer to pipe2(2) for more info on the $flags, but at the time of this writing,
"IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK" and "IO::AIO::O_DIRECT" (Linux 3.4, for
packet-based pipes) were supported.
Example: create a pipe race-free w.r.t. threads and fork:
my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
or die "pipe2: $!\n";
$fh = IO::AIO::memfd_create $pathname[, $flags]
This is a direct interface to the Linux memfd_create(2) system call. The (unhelpful)
default for $flags is 0, but your default should be "IO::AIO::MFD_CLOEXEC".
On success, the new memfd filehandle is returned, otherwise returns "undef". If the
memfd_create syscall is missing, fails with "ENOSYS".
Please refer to memfd_create(2) for more info on this call.
The following $flags values are available: "IO::AIO::MFD_CLOEXEC",
"IO::AIO::MFD_ALLOW_SEALING" and "IO::AIO::MFD_HUGETLB".
Example: create a new memfd.
my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
or die "memfd_create: $!\n";
$fh = IO::AIO::pidfd_open $pid[, $flags]
This is an interface to the Linux pidfd_open(2) system call. The default for $flags is
0.
On success, a new pidfd filehandle is returned (that is already set to close-on-exec),
otherwise returns "undef". If the syscall is missing, fails with "ENOSYS".
Example: open pid 6341 as pidfd.
my $fh = IO::AIO::pidfd_open 6341
or die "pidfd_open: $!\n";
$status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[, $flags]]
This is an interface to the Linux pidfd_send_signal system call. The default for
$siginfo is "undef" and the default for $flags is 0.
Returns the system call status. If the syscall is missing, fails with "ENOSYS".
When specified, $siginfo must be a reference to a hash with one or more of the
following members:
code - the "si_code" member
pid - the "si_pid" member
uid - the "si_uid" member
value_int - the "si_value.sival_int" member
value_ptr - the "si_value.sival_ptr" member, specified as an integer
Example: send a SIGKILL to the specified process.
my $status = IO::AIO::pidfd_send_signal $pidfh, 9, undef
and die "pidfd_send_signal: $!\n";
Example: send a SIGKILL to the specified process with extra data.
my $status = IO::AIO::pidfd_send_signal $pidfh, 9, { code => -1, value_int => 7 }
and die "pidfd_send_signal: $!\n";
$fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
This is an interface to the Linux pidfd_getfd system call. The default for $flags is
0.
On success, returns a dup'ed copy of the target file descriptor (specified as an
integer) returned (that is already set to close-on-exec), otherwise returns "undef".
If the syscall is missing, fails with "ENOSYS".
Example: get a copy of standard error of another process and print soemthing to it.
my $errfh = IO::AIO::pidfd_getfd $pidfh, 2
or die "pidfd_getfd: $!\n";
print $errfh "stderr\n";
$fh = IO::AIO::eventfd [$initval, [$flags]]
This is a direct interface to the Linux eventfd(2) system call. The (unhelpful)
defaults for $initval and $flags are 0 for both.
On success, the new eventfd filehandle is returned, otherwise returns "undef". If the
eventfd syscall is missing, fails with "ENOSYS".
Please refer to eventfd(2) for more info on this call.
The following symbol flag values are available: "IO::AIO::EFD_CLOEXEC",
"IO::AIO::EFD_NONBLOCK" and "IO::AIO::EFD_SEMAPHORE" (Linux 2.6.30).
Example: create a new eventfd filehandle:
$fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
or die "eventfd: $!\n";
$fh = IO::AIO::timerfd_create $clockid[, $flags]
This is a direct interface to the Linux timerfd_create(2) system call. The (unhelpful)
default for $flags is 0, but your default should be "IO::AIO::TFD_CLOEXEC".
On success, the new timerfd filehandle is returned, otherwise returns "undef". If the
timerfd_create syscall is missing, fails with "ENOSYS".
Please refer to timerfd_create(2) for more info on this call.
The following $clockid values are available: "IO::AIO::CLOCK_REALTIME",
"IO::AIO::CLOCK_MONOTONIC" "IO::AIO::CLOCK_CLOCK_BOOTTIME" (Linux 3.15)
"IO::AIO::CLOCK_CLOCK_REALTIME_ALARM" (Linux 3.11) and
"IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM" (Linux 3.11).
The following $flags values are available (Linux 2.6.27): "IO::AIO::TFD_NONBLOCK" and
"IO::AIO::TFD_CLOEXEC".
Example: create a new timerfd and set it to one-second repeated alarms, then wait for
two alarms:
my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
or die "timerfd_create: $!\n";
defined IO::AIO::timerfd_settime $fh, 0, 1, 1
or die "timerfd_settime: $!\n";
for (1..2) {
8 == sysread $fh, my $buf, 8
or die "timerfd read failure\n";
printf "number of expirations (likely 1): %d\n",
unpack "Q", $buf;
}
($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval,
$nbw_value
This is a direct interface to the Linux timerfd_settime(2) system call. Please refer
to its manpage for more info on this call.
The new itimerspec is specified using two (possibly fractional) second values,
$new_interval and $new_value).
On success, the current interval and value are returned (as per "timerfd_gettime"). On
failure, the empty list is returned.
The following $flags values are available: "IO::AIO::TFD_TIMER_ABSTIME" and
"IO::AIO::TFD_TIMER_CANCEL_ON_SET".
See "IO::AIO::timerfd_create" for a full example.
($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
This is a direct interface to the Linux timerfd_gettime(2) system call. Please refer
to its manpage for more info on this call.
On success, returns the current values of interval and value for the given timerfd (as
potentially fractional second values). On failure, the empty list is returned.
EVENT LOOP INTEGRATION
It is recommended to use AnyEvent::AIO to integrate IO::AIO automatically into many event
loops:
# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
use AnyEvent::AIO;
You can also integrate IO::AIO manually into many event loops, here are some examples of
how to do this:
# EV integration
my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
# Event integration
Event->io (fd => IO::AIO::poll_fileno,
poll => 'r',
cb => \&IO::AIO::poll_cb);
# Glib/Gtk2 integration
add_watch Glib::IO IO::AIO::poll_fileno,
in => sub { IO::AIO::poll_cb; 1 };
# Tk integration
Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
readable => \&IO::AIO::poll_cb);
# Danga::Socket integration
Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
\&IO::AIO::poll_cb);
FORK BEHAVIOUR
Usage of pthreads in a program changes the semantics of fork considerably. Specifically,
only async-safe functions can be called after fork. Perl doesn't know about this, so in
general, you cannot call fork with defined behaviour in perl if pthreads are involved.
IO::AIO uses pthreads, so this applies, but many other extensions and (for inexplicable
reasons) perl itself often is linked against pthreads, so this limitation applies to quite
a lot of perls.
This module no longer tries to fight your OS, or POSIX. That means IO::AIO only works in
the process that loaded it. Forking is fully supported, but using IO::AIO in the child is
not.
You might get around by not using IO::AIO before (or after) forking. You could also try to
call the IO::AIO::reinit function in the child:
IO::AIO::reinit
Abandons all current requests and I/O threads and simply reinitialises all data
structures. This is not an operation supported by any standards, but happens to work
on GNU/Linux and some newer BSD systems.
The only reasonable use for this function is to call it after forking, if "IO::AIO"
was used in the parent. Calling it while IO::AIO is active in the process will result
in undefined behaviour. Calling it at any time will also result in any undefined (by
POSIX) behaviour.
LINUX-SPECIFIC CALLS
When a call is documented as "linux-specific" then this means it originated on GNU/Linux.
"IO::AIO" will usually try to autodetect the availability and compatibility of such calls
regardless of the platform it is compiled on, so platforms such as FreeBSD which often
implement these calls will work. When in doubt, call them and see if they fail wth
"ENOSYS".
MEMORY USAGE
Per-request usage:
Each aio request uses - depending on your architecture - around 100-200 bytes of memory.
In addition, stat requests need a stat buffer (possibly a few hundred bytes), readdir
requires a result buffer and so on. Perl scalars and other data passed into aio requests
will also be locked and will consume memory till the request has entered the done state.
This is not awfully much, so queuing lots of requests is not usually a problem.
Per-thread usage:
In the execution phase, some aio requests require more memory for temporary buffers, and
each thread requires a stack and other data structures (usually around 16k-128k, depending
on the OS).
KNOWN BUGS
Known bugs will be fixed in the next release :)
KNOWN ISSUES
Calls that try to "import" foreign memory areas (such as "IO::AIO::mmap" or
"IO::AIO::aio_slurp") do not work with generic lvalues, such as non-created hash slots or
other scalars I didn't think of. It's best to avoid such and either use scalar variables
or making sure that the scalar exists (e.g. by storing "undef") and isn't "funny" (e.g.
tied).
I am not sure anything can be done about this, so this is considered a known issue, rather
than a bug.
SEE ALSO
AnyEvent::AIO for easy integration into event loops, Coro::AIO for a more natural syntax
and IO::FDPass for file descriptor passing.
AUTHOR
Marc Lehmann <schmorp@schmorp.de>
http://home.schmorp.de/