tools/perf/bench/sched-pipe.c | 43 +++++++++++++++++++++++++++++------ 1 file changed, 36 insertions(+), 7 deletions(-)
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>
---
tools/perf/bench/sched-pipe.c | 43 +++++++++++++++++++++++++++++------
1 file changed, 36 insertions(+), 7 deletions(-)
diff --git a/tools/perf/bench/sched-pipe.c b/tools/perf/bench/sched-pipe.c
index 3af6d3c55aba..e2562677df96 100644
--- a/tools/perf/bench/sched-pipe.c
+++ b/tools/perf/bench/sched-pipe.c
@@ -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 @@ static int parse_two_cgroups(const struct option *opt __maybe_unused,
}
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);
--
2.47.0.rc1.288.g06298d1525-googOn Wed, 16 Oct 2024 15:00:09 -0400, Brian Geffon wrote: > 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 > > > [...] Applied to perf-tools-next, thanks! Best regards, Namhyung
On Wed, Oct 16, 2024 at 12:00 PM Brian Geffon <bgeffon@google.com> wrote:
>
> 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>
I liked the commentary in:
https://lore.kernel.org/lkml/ZxAOgj9RWm4NTl9d@google.com/
Thanks,
Ian
> ---
> tools/perf/bench/sched-pipe.c | 43 +++++++++++++++++++++++++++++------
> 1 file changed, 36 insertions(+), 7 deletions(-)
>
> diff --git a/tools/perf/bench/sched-pipe.c b/tools/perf/bench/sched-pipe.c
> index 3af6d3c55aba..e2562677df96 100644
> --- a/tools/perf/bench/sched-pipe.c
> +++ b/tools/perf/bench/sched-pipe.c
> @@ -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 @@ static int parse_two_cgroups(const struct option *opt __maybe_unused,
> }
>
> 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);
>
> --
> 2.47.0.rc1.288.g06298d1525-goog
>
>
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