// SPDX-License-Identifier: GPL-2.0
#ifdef HAVE_EVENTFD_SUPPORT
/*
* Copyright (C) 2018 Davidlohr Bueso.
*
* This program benchmarks concurrent epoll_wait(2) monitoring multiple
* file descriptors under one or two load balancing models. The first,
* and default, is the single/combined queueing (which refers to a single
* epoll instance for N worker threads):
*
* |---> [worker A]
* |---> [worker B]
* [combined queue] .---> [worker C]
* |---> [worker D]
* |---> [worker E]
*
* While the second model, enabled via --multiq option, uses multiple
* queueing (which refers to one epoll instance per worker). For example,
* short lived tcp connections in a high throughput httpd server will
* distribute the accept()'ing connections across CPUs. In this case each
* worker does a limited amount of processing.
*
* [queue A] ---> [worker]
* [queue B] ---> [worker]
* [queue C] ---> [worker]
* [queue D] ---> [worker]
* [queue E] ---> [worker]
*
* Naturally, the single queue will enforce more concurrency on the epoll
* instance, and can therefore scale poorly compared to multiple queues.
* However, this is a benchmark raw data and must be taken with a grain of
* salt when choosing how to make use of sys_epoll.
* Each thread has a number of private, nonblocking file descriptors,
* referred to as fdmap. A writer thread will constantly be writing to
* the fdmaps of all threads, minimizing each threads's chances of
* epoll_wait not finding any ready read events and blocking as this
* is not what we want to stress. The size of the fdmap can be adjusted
* by the user; enlarging the value will increase the chances of
* epoll_wait(2) blocking as the lineal writer thread will take "longer",
* at least at a high level.
*
* Note that because fds are private to each thread, this workload does
* not stress scenarios where multiple tasks are awoken per ready IO; ie:
* EPOLLEXCLUSIVE semantics.
*
* The end result/metric is throughput: number of ops/second where an
* operation consists of:
*
* epoll_wait(2) + [others]
*
* ... where [others] is the cost of re-adding the fd (EPOLLET),
* or rearming it (EPOLLONESHOT).
*
*
* The purpose of this is program is that it be useful for measuring
* kernel related changes to the sys_epoll, and not comparing different
* IO polling methods, for example. Hence everything is very adhoc and
* outputs raw microbenchmark numbers. Also this uses eventfd, similar
* tools tend to use pipes or sockets, but the result is the same.
*/
/* For the CLR_() macros */
#include <string.h>
#include <pthread.h>
#include <unistd.h>
#include <errno.h>
#include <inttypes.h>
#include <signal.h>
#include <stdlib.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/epoll.h>
#include <sys/eventfd.h>
#include <sys/types.h>
#include <perf/cpumap.h>
#include "../util/stat.h"
#include "../util/mutex.h"
#include <subcmd/parse-options.h>
#include "bench.h"
#include <err.h>
#define printinfo(fmt, arg...) \
do { if (__verbose) { printf(fmt, ## arg); fflush(stdout); } } while (0)
static unsigned int nthreads = 0;
static unsigned int nsecs = 8;
static bool wdone, done, __verbose, randomize, nonblocking;
/*
* epoll related shared variables.
*/
/* Maximum number of nesting allowed inside epoll sets */
#define EPOLL_MAXNESTS 4
static int epollfd;
static int *epollfdp;
static bool noaffinity;
static unsigned int nested = 0;
static bool et; /* edge-trigger */
static bool oneshot;
static bool multiq; /* use an epoll instance per thread */
/* amount of fds to monitor, per thread */
static unsigned int nfds = 64;
static struct mutex thread_lock;
static unsigned int threads_starting;
static struct stats throughput_stats;
static struct cond thread_parent, thread_worker;
struct worker {
int tid;
int epollfd; /* for --multiq */
pthread_t thread;
unsigned long ops;
int *fdmap;
};
static const struct option options[] = {
/* general benchmark options */
OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
OPT_UINTEGER('r', "runtime", &nsecs, "Specify runtime (in seconds)"),
OPT_UINTEGER('f', "nfds", &nfds, "Specify amount of file descriptors to monitor for each thread"),
OPT_BOOLEAN( 'n', "noaffinity", &noaffinity, "Disables CPU affinity"),
OPT_BOOLEAN('R', "randomize", &randomize, "Enable random write behaviour (default is lineal)"),
OPT_BOOLEAN( 'v', "verbose", &__verbose, "Verbose mode"),
/* epoll specific options */
OPT_BOOLEAN( 'm', "multiq", &multiq, "Use multiple epoll instances (one per thread)"),
OPT_BOOLEAN( 'B', "nonblocking", &nonblocking, "Nonblocking epoll_wait(2) behaviour"),
OPT_UINTEGER( 'N', "nested", &nested, "Nesting level epoll hierarchy (default is 0, no nesting)"),
OPT_BOOLEAN( 'S', "oneshot", &oneshot, "Use EPOLLONESHOT semantics"),
OPT_BOOLEAN( 'E', "edge", &et, "Use Edge-triggered interface (default is LT)"),
OPT_END()
};
static const char * const bench_epoll_wait_usage[] = {
"perf bench epoll wait <options>",
NULL
};
/*
* Arrange the N elements of ARRAY in random order.
* Only effective if N is much smaller than RAND_MAX;
* if this may not be the case, use a better random
* number generator. -- Ben Pfaff.
*/
static void shuffle(void *array, size_t n, size_t size)
{
char *carray = array;
void *aux;
size_t i;
if (n <= 1)
return;
aux = calloc(1, size);
if (!aux)
err(EXIT_FAILURE, "calloc");
for (i = 1; i < n; ++i) {
size_t j = i + rand() / (RAND_MAX / (n - i) + 1);
j *= size;
memcpy(aux, &carray[j], size);
memcpy(&carray[j], &carray[i*size], size);
memcpy(&carray[i*size], aux, size);
}
free(aux);
}
static void *workerfn(void *arg)
{
int fd, ret, r;
struct worker *w = (struct worker *) arg;
unsigned long ops = w->ops;
struct epoll_event ev;
uint64_t val;
int to = nonblocking? 0 : -1;
int efd = multiq ? w->epollfd : epollfd;
mutex_lock(&thread_lock);
threads_starting--;
if (!threads_starting)
cond_signal(&thread_parent);
cond_wait(&thread_worker, &thread_lock);
mutex_unlock(&thread_lock);
do {
/*
* Block indefinitely waiting for the IN event.
* In order to stress the epoll_wait(2) syscall,
* call it event per event, instead of a larger
* batch (max)limit.
*/
do {
ret = epoll_wait(efd, &ev, 1, to);
} while (ret < 0 && errno == EINTR);
if (ret < 0)
err(EXIT_FAILURE, "epoll_wait");
fd = ev.data.fd;
do {
r = read(fd, &val, sizeof(val));
} while (!done && (r < 0 && errno == EAGAIN));
if (et) {
ev.events = EPOLLIN | EPOLLET;
ret = epoll_ctl(efd, EPOLL_CTL_ADD, fd, &ev);
}
if (oneshot) {
/* rearm the file descriptor with a new event mask */
ev.events |= EPOLLIN | EPOLLONESHOT;
ret = epoll_ctl(efd, EPOLL_CTL_MOD, fd, &ev);
}
ops++;
} while (!done);
if (multiq)
close(w->epollfd);
w->ops = ops;
return NULL;
}
static void nest_epollfd(struct worker *w)
{
unsigned int i;
struct epoll_event ev;
int efd = multiq ? w->epollfd : epollfd;
if (nested > EPOLL_MAXNESTS)
nested = EPOLL_MAXNESTS;
epollfdp = calloc(nested, sizeof(*epollfdp));
if (!epollfdp)
err(EXIT_FAILURE, "calloc");
for (i = 0; i < nested; i++) {
epollfdp[i] = epoll_create(1);
if (epollfdp[i] < 0)
err(EXIT_FAILURE, "epoll_create");
}
ev.events = EPOLLHUP; /* anything */
ev.data.u64 = i; /* any number */
for (i = nested - 1; i; i--) {
if (epoll_ctl(epollfdp[i - 1], EPOLL_CTL_ADD,
epollfdp[i], &ev) < 0)
err(EXIT_FAILURE, "epoll_ctl");
}
if (epoll_ctl(efd, EPOLL_CTL_ADD, *epollfdp, &ev) < 0)
err(EXIT_FAILURE, "epoll_ctl");
}
static void toggle_done(int sig __maybe_unused,
siginfo_t *info __maybe_unused,
void *uc __maybe_unused)
{
/* inform all threads that we're done for the day */
done = true;
gettimeofday(&bench__end, NULL);
timersub(&bench__end, &bench__start, &bench__runtime);
}
static void print_summary(void)
{
unsigned long avg = avg_stats(&throughput_stats);
double stddev = stddev_stats(&throughput_stats);
printf("\nAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
avg, rel_stddev_stats(stddev, avg),
(int)bench__runtime.tv_sec);
}
static int do_threads(struct worker *worker, struct perf_cpu_map *cpu)
{
pthread_attr_t thread_attr, *attrp = NULL;
cpu_set_t *cpuset;
unsigned int i, j;
int ret = 0, events = EPOLLIN;
int nrcpus;
size_t size;
if (oneshot)
events |= EPOLLONESHOT;
if (et)
events |= EPOLLET;
printinfo("starting worker/consumer %sthreads%s\n",
noaffinity ? "":"CPU affinity ",
nonblocking ? " (nonblocking)":"");
if (!noaffinity)
pthread_attr_init(&thread_attr);
nrcpus = cpu__max_cpu().cpu;
cpuset = CPU_ALLOC(nrcpus);
BUG_ON(!cpuset);
size = CPU_ALLOC_SIZE(nrcpus);
for (i = 0; i < nthreads; i++) {
struct worker *w = &worker[i];
if (multiq) {
w->epollfd = epoll_create(1);
if (w->epollfd < 0)
err(EXIT_FAILURE, "epoll_create");
if (nested)
nest_epollfd(w);
}
w->tid = i;
w->fdmap = calloc(nfds, sizeof(int));
if (!w->fdmap)
return 1;
for (j = 0; j < nfds; j++) {
int efd = multiq ? w->epollfd : epollfd;
struct epoll_event ev;
w->fdmap[j] = eventfd(0, EFD_NONBLOCK);
if (w->fdmap[j] < 0)
err(EXIT_FAILURE, "eventfd");
ev.data.fd = w->fdmap[j];
ev.events = events;
ret = epoll_ctl(efd, EPOLL_CTL_ADD,
w->fdmap[j], &ev);
if (ret < 0)
err(EXIT_FAILURE, "epoll_ctl");
}
if (!noaffinity) {
CPU_ZERO_S(size, cpuset);
CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu,
size, cpuset);
ret = pthread_attr_setaffinity_np(&thread_attr, size, cpuset);
if (ret) {
CPU_FREE(cpuset);
err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
}
attrp = &thread_attr;
}
ret = pthread_create(&w->thread, attrp, workerfn,
(void *)(struct worker *) w);
if (ret) {
CPU_FREE(cpuset);
err(EXIT_FAILURE, "pthread_create");
}
}
CPU_FREE(cpuset);
if (!noaffinity)
pthread_attr_destroy(&thread_attr);
return ret;
}
static void *writerfn(void *p)
{
struct worker *worker = p;
size_t i, j, iter;
const uint64_t val = 1;
ssize_t sz;
struct timespec ts = { .tv_sec = 0,
.tv_nsec = 500 };
printinfo("starting writer-thread: doing %s writes ...\n",
randomize? "random":"lineal");
for (iter = 0; !wdone; iter++) {
if (randomize) {
shuffle((void *)worker, nthreads, sizeof(*worker));
}
for (i = 0; i < nthreads; i++) {
struct worker *w = &worker[i];
if (randomize) {
shuffle((void *)w->fdmap, nfds, sizeof(int));
}
for (j = 0; j < nfds; j++) {
do {
sz = write(w->fdmap[j], &val, sizeof(val));
} while (!wdone && (sz < 0 && errno == EAGAIN));
}
}
nanosleep(&ts, NULL);
}
printinfo("exiting writer-thread (total full-loops: %zd)\n", iter);
return NULL;
}
static int cmpworker(const void *p1, const void *p2)
{
struct worker *w1 = (struct worker *) p1;
struct worker *w2 = (struct worker *) p2;
return w1->tid > w2->tid;
}
int bench_epoll_wait(int argc, const char **argv)
{
int ret = 0;
struct sigaction act;
unsigned int i;
struct worker *worker = NULL;
struct perf_cpu_map *cpu;
pthread_t wthread;
struct rlimit rl, prevrl;
argc = parse_options(argc, argv, options, bench_epoll_wait_usage, 0);
if (argc) {
usage_with_options(bench_epoll_wait_usage, options);
exit(EXIT_FAILURE);
}
memset(&act, 0, sizeof(act));
sigfillset(&act.sa_mask);
act.sa_sigaction = toggle_done;
sigaction(SIGINT, &act, NULL);
cpu = perf_cpu_map__new_online_cpus();
if (!cpu)
goto errmem;
/* a single, main epoll instance */
if (!multiq) {
epollfd = epoll_create(1);
if (epollfd < 0)
err(EXIT_FAILURE, "epoll_create");
/*
* Deal with nested epolls, if any.
*/
if (nested)
nest_epollfd(NULL);
}
printinfo("Using %s queue model\n", multiq ? "multi" : "single");
printinfo("Nesting level(s): %d\n", nested);
/* default to the number of CPUs and leave one for the writer pthread */
if (!nthreads)
nthreads = perf_cpu_map__nr(cpu) - 1;
worker = calloc(nthreads, sizeof(*worker));
if (!worker) {
goto errmem;
}
if (getrlimit(RLIMIT_NOFILE, &prevrl))
err(EXIT_FAILURE, "getrlimit");
rl.rlim_cur = rl.rlim_max = nfds * nthreads * 2 + 50;
printinfo("Setting RLIMIT_NOFILE rlimit from %" PRIu64 " to: %" PRIu64 "\n",
(uint64_t)prevrl.rlim_max, (uint64_t)rl.rlim_max);
if (setrlimit(RLIMIT_NOFILE, &rl) < 0)
err(EXIT_FAILURE, "setrlimit");
printf("Run summary [PID %d]: %d threads monitoring%s on "
"%d file-descriptors for %d secs.\n\n",
getpid(), nthreads, oneshot ? " (EPOLLONESHOT semantics)": "", nfds, nsecs);
init_stats(&throughput_stats);
mutex_init(&thread_lock);
cond_init(&thread_parent);
cond_init(&thread_worker);
threads_starting = nthreads;
gettimeofday(&bench__start, NULL);
do_threads(worker, cpu);
mutex_lock(&thread_lock);
while (threads_starting)
cond_wait(&thread_parent, &thread_lock);
cond_broadcast(&thread_worker);
mutex_unlock(&thread_lock);
/*
* At this point the workers should be blocked waiting for read events
* to become ready. Launch the writer which will constantly be writing
* to each thread's fdmap.
*/
ret = pthread_create(&wthread, NULL, writerfn,
(void *)(struct worker *) worker);
if (ret)
err(EXIT_FAILURE, "pthread_create");
sleep(nsecs);
toggle_done(0, NULL, NULL);
printinfo("main thread: toggling done\n");
sleep(1); /* meh */
wdone = true;
ret = pthread_join(wthread, NULL);
if (ret)
err(EXIT_FAILURE, "pthread_join");
/* cleanup & report results */
cond_destroy(&thread_parent);
cond_destroy(&thread_worker);
mutex_destroy(&thread_lock);
/* sort the array back before reporting */
if (randomize)
qsort(worker, nthreads, sizeof(struct worker), cmpworker);
for (i = 0; i < nthreads; i++) {
unsigned long t = bench__runtime.tv_sec > 0 ?
worker[i].ops / bench__runtime.tv_sec : 0;
update_stats(&throughput_stats, t);
if (nfds == 1)
printf("[thread %2d] fdmap: %p [ %04ld ops/sec ]\n",
worker[i].tid, &worker[i].fdmap[0], t);
else
printf("[thread %2d] fdmap: %p ... %p [ %04ld ops/sec ]\n",
worker[i].tid, &worker[i].fdmap[0],
&worker[i].fdmap[nfds-1], t);
}
print_summary();
close(epollfd);
perf_cpu_map__put(cpu);
for (i = 0; i < nthreads; i++)
free(worker[i].fdmap);
free(worker);
return ret;
errmem:
err(EXIT_FAILURE, "calloc");
}
#endif // HAVE_EVENTFD_SUPPORT
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