NAME

IO::Uring - io_uring for Perl

VERSION

version 0.001

SYNOPSIS

my $ring = IO::Uring->new(32);
my $buffer = "\0" x 4096;
$ring->recv($fh, $buffer, MSG_WAITALL, 0, sub($res, $flags) { ... });
$ring->send($fh, $buffer, 0, 0, sub($res, $flags) { ... });
$ring->run_once while 1;

DESCRIPTION

This module is a low-level interface to io_uring, Linux's new asynchronous I/O interface drastically reducing the number of system calls needed to perform I/O. Unlike previous models such as epoll it's based on a proactor model instead of a reactor model, meaning that you schedule asynchronous actions and then get notified by a callback when the action has completed.

Generally speaking, the methods of this class match a system call 1-on-1 (e.g. recv), except that they have two additional argument:

1. The submission flags. In particular this allows you to chain actions.
2. A callback. This callback received two integer arguments: a result (on error typically a negative errno value), and the completion flags. This callback will be kept alive by thos module, any other resources that need to be kept alive should be captured by it.

All event methods return an identifier that can be used with cancel.

Note: this is an early release and this module should still be regarded experimental. Backwards compatibility is not yet guaranteed.

METHODS

new($queue_size)

This creates a new uring object, with the given submission queue size.

run_once($min_events = 1)

This will submit all pending requests, and process at least $min_events completed (but up to $queue_size) events.

accept($sock, $flags, $s_flags, $callback)

Equivalent to accept4($fh, $flags).

cancel($identifier, $flags, $s_flags, $callback = undef)

This cancels a pending request. $identifier should usually be the value return by a previous event method. $flags is usually 0, but be IORING_ASYNC_CANCEL_ALL, IORING_ASYNC_CANCEL_FD or IORING_ASYNC_CANCEL_ANY. Note that unlike most event methods the $callback is allowed to be empty.

close($fh, $s_flags, $callback)

This closes the filedescriptor $fh.

connect($sock, $sockaddr, $s_flags, $callback)

Connect socket $sock to address $sockaddr.

fallocate($fh, $offset, $length, $s_flags, $callback)

This allocates disk space in $fh for $offset and $length.

fsync($fh, $flags, $s_flags, $callback)

This will synchronize a file's in-core state with storage device. flags may be 0 or IORING_FSYNC_DATASYNC.

ftruncate($fh, $length, $s_flags, $callback)

Truncate $fh to length $length.

link($old_path, $new_path, $flags, $s_flags, $callback)

This links the file at $new_path to $old_path.

linkat($old_dir, $old_path, $new_dir, $new_path, $flags, $s_flags, $callback)

This links the file at $new_path in $new_dir (a directory handle) to $old_path in $old_dir.

link_timeout($time_spec, $flags, $s_flags, $callback = undef)

This prepares a timeout request for linked submissions (using the IOSQE_IO_LINK/IOSQE_IO_HARDLINK submission flags). $timespec must refer to a Time::Spec object that must be kept alive through the callback. $flags is a bit set that may contain any of the following values: IORING_TIMEOUT_ABS, IORING_TIMEOUT_BOOTTIME, IORING_TIMEOUT_REALTIME, IORING_TIMEOUT_ETIME_SUCCESS, IORING_TIMEOUT_MULTISHOT.

Like cancel and timeout_remove, the $callback is optional.

mkdir($path, $mode, $s_flags, $callback)

Make a new directory at $path with mode $mode.

mkdirat($dirhandle, $path, $mode, $s_flags, $callback)

Make a new directory at $path under $dirhandle with mode $mode.

nop($s_flags, $callback)

This executes a no-op.

open($path, $flags, $mode, $s_flags, $callback)

Open a file at $path with $flags and mode.

openat($dirhandle, $path, $flags, $mode, $s_flags, $callback)

Open a file at $path under $dirhandle with $flags and mode.

poll($fh, $mask, $s_flags, $callback)

This will poll file handle $fh once. $mask can have the same values as synchronous poll (e.g. POLLIN, POLLOUT).

poll_multishot($fh, $mask, $s_flags, $callback)

This will poll file handle $fh and repeatedly call $callback whenever new data is available. $mask can have the same values as synchronous poll (e.g. POLLIN, POLLOUT).

shutdown($fh, $how, $s_flags, $callback)

This shuts down a part of a connection, the same way the core builtin shutdown($fh, $how) does.

splice($fh_in, $off_in, $fh_out, $off_out, $nbytes, $flags, $s_flags, $callback)

This moves data between two file descriptors without copying between kernel address space and user address space. It transfers up to size bytes of data from the file descriptor $fh_in to the file descriptor fh_out, where one of the file descriptors must refer to a pipe.

For a pipe file descriptor the associated offset must be -1. If set it will be used as the offset in the file or block device to start the read.

flags must currently be 0.

sync_file_range($fh, $length, $offset, $flags, $s_flags, $callback)

This synchronises the given range to disk. $flags must currently be 0.

read($fh, $buffer, $offset, $s_flags, $callback)

Equivalent to pread($fh, $buffer, $offset). The buffer must be preallocated to the desired size, the callback received the number of bytes in it that are actually written to. The buffer must be kept alive, typically by enclosing over it in the callback.

recv($sock, $buffer, $flags, $s_flags, $callback)

Equivalent to recv($fh, $buffer, $flags). The buffer must be preallocated to the desired size, the callback received the number of bytes in it that are actually written to. The buffer must be kept alive, typically by enclosing over it in the callback.

rename($old_path, $new_path, $flags, $s_flags, $callback)

This renames the file at $old_path to $new_path.

renameat($old_dir, $old_path, $new_dir, $new_path, $flags, $s_flags, $callback)

This renames the file at $old_path in $old_dir (a directory handle) to $new_path in $new_dir.

send($sock, $buffer, $flags, $s_flags, $callback)

Equivalent to send($fh, $buffer, $flags). The buffer must be kept alive, typically by enclosing over it in the callback.

tee($fh_in, $fh_out, $nbytes, $flags, $callback)

This prepares a tee request. This will use as input the file descriptor $fh_in and as output the file descriptor $fh_out duplicating $nbytes bytes worth of data. $flags are modifier flags for the operation and must currently be 0.

timeout($timespec, $count, $flags, $s_flags, $callback)

This creates a timeout. $timespec must refer to a Time::Spec object that must be kept alive through the callback. $count is the number of events that should be waited on, typically it would be 0. $flags is a bit set that may contain any of the following values: IORING_TIMEOUT_ABS, IORING_TIMEOUT_BOOTTIME, IORING_TIMEOUT_REALTIME, IORING_TIMEOUT_ETIME_SUCCESS, IORING_TIMEOUT_MULTISHOT.

timeout_remove($id, $flags, $s_flags, $callback = undef)

Remove a timeout identified by $id. $flags is currently unused and must be 0. Like cancel and link_timeout, the callback is optional.

timeout_update($id, $timespec, $flags, $s_flags, $callback)

This updates the timer identifiers by $id. timespec and flags have the same meaning as in timeout.

unlink($path, $mode, $s_flags, $callback)

Remove a file or directory at $path with flags $flags.

unlinkat($dirhandle, $path, $mode, $s_flags, $callback)

Remove a file or directory at $path under $dirhandle with flags $flags.

waitid($id_type, $id, $info, $options, $flags, $s_flags, $callback)

This waits for another process. $id_type specifies the type of ID used and must be one of P_PID ($id is a PID), P_PGID ($id is a process group), P_PIDFD ($id is a PID fd) or P_ALL ($id is ignored, wait for any child). $info must be a Signal::Info object that must be kept alive through the callback, it will contain the result of the event. $options is a bitset of WEXITED, WSTOPPED WCONTINUED, WNOWAIT; typically it would be WEXITED. $flags is currently unused and must be 0. When the callback is triggered the following entries of $info will be set: pid, uid, signo (will always be SIGCHLD), status and code (CLD_EXITED, CLD_KILLED)

write($fh, $buffer, $offset, $s_flags, $callback)

Equivalent to send($fh, $buffer, $flags). The buffer must be kept alive, typically by enclosing over it in the callback.

FLAGS

The following flags are all optionally exported:

Submission flags:

These flags are passed to all event methods, and affect how the submission is processed.

IOSQE_ASYNC

Normal operation for io_uring is to try and issue an sqe as non-blocking first, and if that fails, execute it in an async manner. To support more efficient overlapped operation of requests that the application knows/assumes will always (or most of the time) block, the application can ask for an sqe to be issued async from the start. Note that this flag immediately causes the SQE to be offloaded to an async helper thread with no initial non-blocking attempt. This may be less efficient and should not be used liberally or without understanding the performance and efficiency tradeoffs.
IOSQE_IO_LINK

When this flag is specified, the SQE forms a link with the next SQE in the submission ring. That next SQE will not be started before the previous request completes. This, in effect, forms a chain of SQEs, which can be arbitrarily long. The tail of the chain is denoted by the first SQE that does not have this flag set. Chains are not supported across submission boundaries. Even if the last SQE in a submission has this flag set, it will still terminate the current chain. This flag has no effect on previous SQE submissions, nor does it impact SQEs that are outside of the chain tail. This means that multiple chains can be executing in parallel, or chains and individual SQEs. Only members inside the chain are serialized. A chain of SQEs will be broken if any request in that chain ends in error.
IOSQE_IO_HARDLINK

Like IOSQE_IO_LINK , except the links aren't severed if an error or unexpected result occurs.
IOSQE_IO_DRAIN

When this flag is specified, the SQE will not be started before previously submitted SQEs have completed, and new SQEs will not be started before this one completes.

Completion flags

These are values set in the $flags arguments of the event callbacks. They include:

IORING_CQE_F_MORE

If set, the application should expect more completions from the request. This is used for requests that can generate multiple completions, such as multi-shot requests, receive, or accept.
IORING_CQE_F_SOCK_NONEMPTY

If set, upon receiving the data from the socket in the current request, the socket still had data left on completion of this request.

Event specific flags

cancel

IORING_ASYNC_CANCEL_ALL

Cancel all requests that match the given criteria, rather than just canceling the first one found. Available since 5.19.
IORING_ASYNC_CANCEL_FD

Match based on the file descriptor used in the original request rather than the user_data. Available since 5.19.
IORING_ASYNC_CANCEL_ANY

Match any request in the ring, regardless of user_data or file descriptor. Can be used to cancel any pending request in the ring. Available since 5.19.

fsync

The only allowed flag value for fsync:

IORING_FSYNC_DATASYNC

If set fsync will do an fdatasync instead: not sync if only metadata has changed.

remove / removeat

RENAME_EXCHANGE

Atomically exchange oldpath and newpath. Both pathnames must exist but may be of different types (e.g., one could be a non-empty directory and the other a symbolic link).
RENAME_NOREPLACE

Don't overwrite newpath of the rename. Return an error if newpath already exists.

RENAME_NOREPLACE can't be employed together with RENAME_EXCHANGE. RENAME_NOREPLACE requires support from the underlying filesystem.

timeout

IORING_TIMEOUT_ABS

The value specified in ts is an absolute value rather than a relative one.
IORING_TIMEOUT_BOOTTIME

The boottime clock source should be used.
IORING_TIMEOUT_REALTIME

The realtime clock source should be used.
IORING_TIMEOUT_ETIME_SUCCESS

Consider an expired timeout a success in terms of the posted completion. This means it will not sever dependent links, as a failed request normally would. The posted CQE result code will still contain -ETIME in the res value.
IORING_TIMEOUT_MULTISHOT

The request will return multiple timeout completions. The completion flag IORING_CQE_F_MORE is set if more timeouts are expected. The value specified in count is the number of repeats. A value of 0 means the timeout is indefinite and can only be stopped by a removal request. Available since the 6.4 kernel.

unlink / unlinkat

AT_REMOVEDIR

If the AT_REMOVEDIR flag is specified, unlink / unlinkat performs the equivalent of rmdir(2) on pathname.

waitid

waitid has various constants defined for it. The following values are defined for the $idtype:

P_PID

This indicated the identifier is a process identifier.
P_PGID

This indicated the identifier is a process group identifier.
P_PIDFD

This indicated the identifier is a pidfd.
P_ALL

This indicated the identifier will be ignored and any child is waited upon.

The following constants are defined for the $options argument:

WEXITED

Wait for children that have terminated.
WSTOPPED

Wait for children that have been stopped by delivery of a signal.
WCONTINUED

Wait for (previously stopped) children that have been resumed by delivery of SIGCONT.
WNOWAIT

Leave the child in a waitable state; a later wait call can be used to again retrieve the child status information.

AUTHOR

Leon Timmermans <fawaka@gmail.com>

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

To install IO::Uring, copy and paste the appropriate command in to your terminal.

cpanm

cpanm IO::Uring

CPAN shell

perl -MCPAN -e shell
install IO::Uring

For more information on module installation, please visit the detailed CPAN module installation guide.

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