ring-buffer-benchmark: Add parameters to set produce/consumer priorities

Running the ring-buffer-benchmark's threads at the lowest priority may
work well for keeping it in the background, but it is not appropriate
for the benchmarks.

This patch adds 4 parameters to the module:

  consumer_fifo
  consumer_nice
  producer_fifo
  producer_nice

By default the consumer and producer still run at nice +19.

If the *_fifo options are set, they will override the *_nice values.

 modprobe ring_buffer_benchmark consumer_nice=0 producer_fifo=10

The above will set the consumer thread to a nice value of 0, and
the producer thread to a RT SCHED_FIFO priority of 10.

Note, this patch also fixes a bug where calling set_user_nice on the
consumer thread would oops the kernel when the parameter "disable_reader"
is set.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 56 insertions, 2 deletions

diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index 3875d49da990..b2477caf09c2 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -39,6 +39,24 @@ static int write_iteration = 50;
 module_param(write_iteration, uint, 0644);
 MODULE_PARM_DESC(write_iteration, "# of writes between timestamp readings");
 
+static int producer_nice = 19;
+static int consumer_nice = 19;
+
+static int producer_fifo = -1;
+static int consumer_fifo = -1;
+
+module_param(producer_nice, uint, 0644);
+MODULE_PARM_DESC(producer_nice, "nice prio for producer");
+
+module_param(consumer_nice, uint, 0644);
+MODULE_PARM_DESC(consumer_nice, "nice prio for consumer");
+
+module_param(producer_fifo, uint, 0644);
+MODULE_PARM_DESC(producer_fifo, "fifo prio for producer");
+
+module_param(consumer_fifo, uint, 0644);
+MODULE_PARM_DESC(consumer_fifo, "fifo prio for consumer");
+
 static int read_events;
 
 static int kill_test;
@@ -270,6 +288,27 @@ static void ring_buffer_producer(void)
 
         if (kill_test)
                 trace_printk("ERROR!\n");
+
+        if (!disable_reader) {
+                if (consumer_fifo < 0)
+                        trace_printk("Running Consumer at nice: %d\n",
+                                     consumer_nice);
+                else
+                        trace_printk("Running Consumer at SCHED_FIFO %d\n",
+                                     consumer_fifo);
+        }
+        if (producer_fifo < 0)
+                trace_printk("Running Producer at nice: %d\n",
+                             producer_nice);
+        else
+                trace_printk("Running Producer at SCHED_FIFO %d\n",
+                             producer_fifo);
+
+        /* Let the user know that the test is running at low priority */
+        if (producer_fifo < 0 && consumer_fifo < 0 &&
+            producer_nice == 19 && consumer_nice == 19)
+                trace_printk("WARNING!!! This test is running at lowest priority.\n");
+
         trace_printk("Time:     %lld (usecs)\n", time);
         trace_printk("Overruns: %lld\n", overruns);
         if (disable_reader)
@@ -402,8 +441,23 @@ static int __init ring_buffer_benchmark_init(void)
         /*
          * Run them as low-prio background tasks by default:
          */
-        set_user_nice(consumer, 19);
-        set_user_nice(producer, 19);
+        if (!disable_reader) {
+                if (consumer_fifo >= 0) {
+                        struct sched_param param = {
+                                .sched_priority = consumer_fifo
+                        };
+                        sched_setscheduler(consumer, SCHED_FIFO, &param);
+                } else
+                        set_user_nice(consumer, consumer_nice);
+        }
+
+        if (producer_fifo >= 0) {
+                struct sched_param param = {
+                        .sched_priority = consumer_fifo
+                };
+                sched_setscheduler(producer, SCHED_FIFO, &param);
+        } else
+                set_user_nice(producer, producer_nice);
 
         return 0;