[PATCH v2] perf: sched-pipe add support for packet I/O mode

From: Shuah Khan
Date: Wed Sep 28 2016 - 11:18:38 EST


Add support to run sched-pipe benchmark test on pipe in packet I/O mode.
In packet I/O mode, each write() to the pipe is handled as a separate
packet and each read() from the pipe will read one packet at a time.

In the kernel, packet_pipe_buf_ops get used in this mode and pipe_write()
and pipe_read() handle this as a special case. As a result, it is helpful
to add support for benchmarking pipe I/O in packet mode.

Signed-off-by: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>
---
Changes since v1:
- Fixed comment block style
- Updated change log to include packet I/O mode details

tools/perf/bench/sched-pipe.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

diff --git a/tools/perf/bench/sched-pipe.c b/tools/perf/bench/sched-pipe.c
index 1dc2d13..10243b6 100644
--- a/tools/perf/bench/sched-pipe.c
+++ b/tools/perf/bench/sched-pipe.c
@@ -41,9 +41,17 @@ static int loops = LOOPS_DEFAULT;
/* Use processes by default: */
static bool threaded;

+/*
+ * Use non-packet (normal) I/O mode by default.
+ * In packet mode, each write is a separate packet.
+ */
+static bool packet_mode;
+
static const struct option options[] = {
OPT_INTEGER('l', "loop", &loops, "Specify number of loops"),
OPT_BOOLEAN('T', "threaded", &threaded, "Specify threads/process based task setup"),
+ OPT_BOOLEAN('P', "packet mode", &packet_mode,
+ "Specify packet I/O mode - "),
OPT_END()
};

@@ -83,6 +91,7 @@ int bench_sched_pipe(int argc, const char **argv, const char *prefix __maybe_unu
unsigned long long result_usec = 0;
int nr_threads = 2;
int t;
+ int flags = 0;

/*
* why does "ret" exist?
@@ -94,6 +103,18 @@ int bench_sched_pipe(int argc, const char **argv, const char *prefix __maybe_unu

argc = parse_options(argc, argv, options, bench_sched_pipe_usage, 0);

+ if (packet_mode) {
+ /* BUG_ON doesn't make sense exit if pipe2() fails */
+ flags = O_DIRECT;
+ ret = pipe2(pipe_1, flags);
+ if (ret)
+ exit(1);
+ ret = pipe2(pipe_2, flags);
+ if (ret)
+ exit(1);
+ printf("Running sched-pipe in packet I/O mode\n\n");
+ }
+
BUG_ON(pipe(pipe_1));
BUG_ON(pipe(pipe_2));

--
2.7.4