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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | SEE ALSO | COLOPHON |
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io_uring_prep_epoll_wait(3) liburing Manual io_uring_prep_epoll_wait(3)
io_uring_prep_epoll_wait - prepare an epoll wait request
#include <sys/epoll.h>
#include <liburing.h>
void io_uring_prep_epoll_wait(struct io_uring_sqe *sqe,
int fd,
struct epoll_event *events,
int maxevents,
unsigned flags );"
The io_uring_prep_epoll_wait(3) function prepares an epoll_wait
request. The submission queue entry sqe is setup to wait on a
maximum of maxevents events on the epoll file descriptor indicated
by fd, and filling the received events into the memory pointed to
by events.
This function prepares an async epoll_wait(2) request. See that
man page for details. The use case is mostly for legacy event
loops, where certain file descriptors may still be using epoll for
readiness notifications. Normally this would necessitate using
epoll_wait with the io_uring fd added to that set as well, which
is suboptimal as epoll doesn't provide the same kind of fine
grained batch control and wakeup reductions that io_uring does. By
using io_uring to read epoll events, the event loop can be
entirely switched to io_uring, and reap the benefits of batch
waiting and context switch reductions.
None
The CQE res field will contain the result of the operation. See
the related man page for details on possible values. Note that
where synchronous system calls will return -1 on failure and set
errno to the actual error value, io_uring never uses errno.
Instead it returns the negated errno directly in the CQE res
field.
io_uring_get_sqe(3), io_uring_submit(3), epoll_wait(2)
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 io-uring@vger.kernel.org. This page
was obtained from the project's upstream Git repository
⟨https://github.com/axboe/liburing⟩ on 2025-08-11. (At that time,
the date of the most recent commit that was found in the
repository was 2025-08-02.) 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
man-pages@man7.org
liburing-2.10 March 6, 2025 io_uring_prep_epoll_wait(3)
Pages that refer to this page: io_uring_prep_epoll_wait(3)
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HTML rendering created 2025-09-06 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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