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perf tools: sched-pipe bench: add (-n) nonblocking benchmark

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The -n mode will benchmark pipes in a non-blocking mode using
epoll_wait.

This specific mode was added to demonstrate the broken sync nature
of epoll: https://lore.kernel.org/lkml/20240426-zupfen-jahrzehnt-5be786bcdf04@brauner

Signed-off-by: Brian Geffon <bgeffon@google.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20241016190009.866615-1-bgeffon@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Brian Geffon 2024-10-16 15:00:09 -04:00 committed by Namhyung Kim
parent 915a377627
commit 3e2d4df574
1 changed files with 36 additions and 7 deletions
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43
tools/perf/bench/sched-pipe.c
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@ -23,6 +23,7 @@
#include <errno.h>
#include <fcntl.h>
#include <assert.h>
#include <sys/epoll.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/syscall.h>
@ -34,6 +35,8 @@ struct thread_data {
int nr;
int pipe_read;
int pipe_write;
struct epoll_event epoll_ev;
int epoll_fd;
bool cgroup_failed;
pthread_t pthread;
};
@ -44,6 +47,7 @@ static int loops = LOOPS_DEFAULT;
/* Use processes by default: */
static bool threaded;
static bool nonblocking;
static char *cgrp_names[2];
static struct cgroup *cgrps[2];
@ -81,6 +85,7 @@ out:
}
static const struct option options[] = {
OPT_BOOLEAN('n', "nonblocking", &nonblocking, "Use non-blocking operations"),
OPT_INTEGER('l', "loop", &loops, "Specify number of loops"),
OPT_BOOLEAN('T', "threaded", &threaded, "Specify threads/process based task setup"),
OPT_CALLBACK('G', "cgroups", NULL, "SEND,RECV",
@ -165,11 +170,25 @@ static void exit_cgroup(int nr)
free(cgrp_names[nr]);
}
static inline int read_pipe(struct thread_data *td)
{
int ret, m;
retry:
if (nonblocking) {
ret = epoll_wait(td->epoll_fd, &td->epoll_ev, 1, -1);
if (ret < 0)
return ret;
}
ret = read(td->pipe_read, &m, sizeof(int));
if (nonblocking && ret < 0 && errno == EWOULDBLOCK)
goto retry;
return ret;
}
static void *worker_thread(void *__tdata)
{
struct thread_data *td = __tdata;
int m = 0, i;
int ret;
int i, ret, m = 0;
ret = enter_cgroup(td->nr);
if (ret < 0) {
@ -177,16 +196,23 @@ static void *worker_thread(void *__tdata)
return NULL;
}
if (nonblocking) {
td->epoll_ev.events = EPOLLIN;
td->epoll_fd = epoll_create(1);
BUG_ON(td->epoll_fd < 0);
BUG_ON(epoll_ctl(td->epoll_fd, EPOLL_CTL_ADD, td->pipe_read, &td->epoll_ev) < 0);
}
for (i = 0; i < loops; i++) {
if (!td->nr) {
ret = read(td->pipe_read, &m, sizeof(int));
ret = read_pipe(td);
BUG_ON(ret != sizeof(int));
ret = write(td->pipe_write, &m, sizeof(int));
BUG_ON(ret != sizeof(int));
} else {
ret = write(td->pipe_write, &m, sizeof(int));
BUG_ON(ret != sizeof(int));
ret = read(td->pipe_read, &m, sizeof(int));
ret = read_pipe(td);
BUG_ON(ret != sizeof(int));
}
}
@ -209,13 +235,16 @@ int bench_sched_pipe(int argc, const char **argv)
* discarding returned value of read(), write()
* causes error in building environment for perf
*/
int __maybe_unused ret, wait_stat;
int __maybe_unused ret, wait_stat, flags = 0;
pid_t pid, retpid __maybe_unused;
argc = parse_options(argc, argv, options, bench_sched_pipe_usage, 0);
BUG_ON(pipe(pipe_1));
BUG_ON(pipe(pipe_2));
if (nonblocking)
flags |= O_NONBLOCK;
BUG_ON(pipe2(pipe_1, flags));
BUG_ON(pipe2(pipe_2, flags));
gettimeofday(&start, NULL);