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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | SEE ALSO | COLOPHON |
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io_uring_sqe_set_flags(3) liburing Manual io_uring_sqe_set_flags(3)
io_uring_sqe_set_flags - set flags for submission queue entry
#include <liburing.h>
void io_uring_sqe_set_flags(struct io_uring_sqe *sqe,
unsigned flags);
The io_uring_sqe_set_flags(3) function allows the caller to
change the behavior of the submission queue entry by specifying
flags. It enables the flags belonging to the sqe submission queue
entry param.
flags is a bit mask of 0 or more of the following values ORed
together:
IOSQE_FIXED_FILE
The file descriptor in the SQE refers to the index of a
previously registered file or direct file descriptor, not
a normal file descriptor.
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.
IOSQE_CQE_SKIP_SUCCESS
Request that no CQE be generated for this request, if it
completes successfully. This can be useful in cases where
the application doesn't need to know when a specific
request completed, if it completed successfully.
IOSQE_BUFFER_SELECT
If set, and if the request types supports it, select an IO
buffer from the indicated buffer group. This can be used
with requests that read or receive data from a file or
socket, where buffer selection is deferred until the
kernel is ready to transfer data, instead of when the IO
is originally submitted. The application must also set the
buf_group field in the SQE, indicating which previously
registered buffer group to select a buffer from.
None
io_uring_submit(3), io_uring_register(3)
io_uring_register_buffers(3) io_uring_register_buf_ring(3)
This page is part of the liburing (A library for io_uring)
project. Information about the project can be found at
⟨https://github.com/axboe/liburing⟩. If you have a bug report for
this manual page, send it to [email protected]. This page
was obtained from the project's upstream Git repository
⟨https://github.com/axboe/liburing⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-03.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
liburing-2.1 January 25, 2022 io_uring_sqe_set_flags(3)
Pages that refer to this page: io_uring_sqe_set_flags(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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