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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |STANDARDS |HISTORY |EXAMPLES |SEE ALSO |COLOPHON | |
ioctl_eventpoll(2) System Calls Manualioctl_eventpoll(2)ioctl_eventpoll, EPIOCSPARAMS, EPIOCGPARAMS - ioctl() operations for epoll file descriptors
Standard C library (libc,-lc)
#include <sys/epoll.h>/* Definition ofEPIOC*constants */#include <sys/ioctl.h>int ioctl(intfd, EPIOCSPARAMS, const struct epoll_params *argp);int ioctl(intfd, 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 theepoll_params structure to configure the operation of epoll. Refer to the structure description below to learn what configuration is supported.EPIOCGPARAMS Get the currentepoll_params configuration settings. All operations documented above must be performed on an epoll file descriptor, which can be obtained with a call toepoll_create(2) orepoll_create1(2).The epoll_params structureargp.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 exceedINT_MAX.argp.busy_poll_budget denotes the maximum number of packets that the network stack will retrieve on each poll attempt. This value cannot exceedNAPI_POLL_WEIGHT(which is 64 as of Linux 6.9), unless the process is run withCAP_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, anderrno is set to indicate the error.
EOPNOTSUPP The kernel was not compiled with busy poll support.EINVALfd is not a valid file descriptor.EINVALargp.__pad is not zero.EINVALargp.busy_poll_usecs exceedsINT_MAX.EINVALargp.prefer_busy_poll is not 0 or 1.EPERMThe process is being run withoutCAP_NET_ADMINand the specifiedargp.busy_poll_budget exceedsNAPI_POLL_WEIGHT.EFAULTargp 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.rstlinux.git/Documentation/admin-guide/sysctl/net.rst
This page is part of theman-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-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. 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 isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17ioctl_eventpoll(2)Pages that refer to this page:epoll_create(2), epoll_ctl(2), ioctl(2), epoll(7)
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