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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | EXAMPLES | SEE ALSO | COLOPHON |
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ioctl_eventpoll(2) System Calls Manual ioctl_eventpoll(2)
ioctl_eventpoll, EPIOCSPARAMS, EPIOCGPARAMS - ioctl() operations
for epoll file descriptors
Standard C library (libc, -lc)
#include <sys/epoll.h> /* Definition of EPIOC* constants */
#include <sys/ioctl.h>
int ioctl(int fd, EPIOCSPARAMS, const struct epoll_params *argp);
int ioctl(int fd, EPIOCGPARAMS, struct epoll_params *argp);
#include <sys/epoll.h>
struct epoll_params {
uint32_t busy_poll_usecs; /* Number of usecs to busy poll */
uint16_t busy_poll_budget; /* Max packets per poll */
uint8_t prefer_busy_poll; /* Boolean preference */
/* pad the struct to a multiple of 64bits */
uint8_t __pad; /* Must be zero */
};
EPIOCSPARAMS
Set the epoll_params structure to configure the operation
of epoll. Refer to the structure description below to
learn what configuration is supported.
EPIOCGPARAMS
Get the current epoll_params configuration settings.
All operations documented above must be performed on an epoll
file descriptor, which can be obtained with a call to
epoll_create(2) or epoll_create1(2).
The epoll_params structure
argp.busy_poll_usecs denotes the number of microseconds that the
network stack will busy poll. During this time period, the
network device will be polled repeatedly for packets. This value
cannot exceed INT_MAX.
argp.busy_poll_budget denotes the maximum number of packets that
the network stack will retrieve on each poll attempt. This value
cannot exceed NAPI_POLL_WEIGHT (which is 64 as of Linux 6.9),
unless the process is run with CAP_NET_ADMIN.
argp.prefer_busy_poll is a boolean field and must be either 0
(disabled) or 1 (enabled). If enabled, this indicates to the
network stack that busy poll is the preferred method of
processing network data and the network stack should give the
application the opportunity to busy poll. Without this option,
very busy systems may continue to do network processing via the
normal method of IRQs triggering softIRQ and NAPI.
argp.__pad must be zero.
On success, 0 is returned. On failure, -1 is returned, and errno
is set to indicate the error.
EOPNOTSUPP
The kernel was not compiled with busy poll support.
EINVAL fd is not a valid file descriptor.
EINVAL argp.__pad is not zero.
EINVAL argp.busy_poll_usecs exceeds INT_MAX.
EINVAL argp.prefer_busy_poll is not 0 or 1.
EPERM The process is being run without CAP_NET_ADMIN and the
specified argp.busy_poll_budget exceeds NAPI_POLL_WEIGHT.
EFAULT argp is an invalid address.
Linux.
Linux 6.9. glibc 2.40.
/* Code to set the epoll params to enable busy polling */
int epollfd = epoll_create1(0);
struct epoll_params params;
if (epollfd == -1) {
perror("epoll_create1");
exit(EXIT_FAILURE);
}
memset(¶ms, 0, sizeof(struct epoll_params));
params.busy_poll_usecs = 25;
params.busy_poll_budget = 8;
params.prefer_busy_poll = 1;
if (ioctl(epollfd, EPIOCSPARAMS, ¶ms) == -1) {
perror("ioctl");
exit(EXIT_FAILURE);
}
/* Code to show how to retrieve the current settings */
memset(¶ms, 0, sizeof(struct epoll_params));
if (ioctl(epollfd, EPIOCGPARAMS, ¶ms) == -1) {
perror("ioctl");
exit(EXIT_FAILURE);
}
/* params struct now contains the current parameters */
fprintf(stderr, "epoll usecs: %lu\n", params.busy_poll_usecs);
fprintf(stderr, "epoll packet budget: %u\n", params.busy_poll_budget);
fprintf(stderr, "epoll prefer busy poll: %u\n", params.prefer_busy_poll);
ioctl(2), epoll_create(2), epoll_create1(2), epoll(7)
linux.git/Documentation/networking/napi.rst
linux.git/Documentation/admin-guide/sysctl/net.rst
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
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⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
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part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.9.1 2024-06-17 ioctl_eventpoll(2)
Pages that refer to this page: epoll_create(2), epoll_ctl(2), ioctl(2), epoll(7)
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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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