ioctl_eventpoll, EPIOCSPARAMS, EPIOCGPARAMS - ioctl() operations for epoll file descriptors

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). Theepoll_paramsstructureargp.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.

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 exceeds INT_MAX. EINVALargp.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. EFAULTargp is an invalid address.

/* 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(&params, 0, sizeof(struct epoll_params)); params.busy_poll_usecs = 25; params.busy_poll_budget = 8; params.prefer_busy_poll = 1; if (ioctl(epollfd, EPIOCSPARAMS, &params) == -1) { perror("ioctl"); exit(EXIT_FAILURE); } /* Code to show how to retrieve the current settings */ memset(&params, 0, sizeof(struct epoll_params)); if (ioctl(epollfd, EPIOCGPARAMS, &params) == -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);

Linux 6.9. glibc 2.40.

Standard C library (libc, -lc)

ioctl_eventpoll, EPIOCSPARAMS, EPIOCGPARAMS - ioctl() operations for epoll file descriptors

On success, 0 is returned. On failure, -1 is returned, and errno is set to indicate the error.

ioctl(2), epoll_create(2), epoll_create1(2), epoll(7) linux.git/Documentation/networking/napi.rstlinux.git/Documentation/admin-guide/sysctl/net.rst Linux man-pages 6.9.1 2024-06-17 ioctl_eventpoll(2)

Linux.

#include<sys/epoll.h> /* Definition of EPIOC* constants */ #include<sys/ioctl.h>intioctl(intfd,EPIOCSPARAMS,conststructepoll_params*argp);intioctl(intfd,EPIOCGPARAMS,structepoll_params*argp);#include<sys/epoll.h>structepoll_params{uint32_tbusy_poll_usecs; /* Number of usecs to busy poll */ uint16_tbusy_poll_budget; /* Max packets per poll */ uint8_tprefer_busy_poll; /* Boolean preference */ /* pad the struct to a multiple of 64bits */ uint8_t__pad; /* Must be zero */ };