generate preemptions and migrations with equal probability

1 files changed, 13 insertions, 2 deletions

diff --git a/bin/cache_cost.c b/bin/cache_cost.c
index 808ca33..db395e4 100644
--- a/bin/cache_cost.c
+++ b/bin/cache_cost.c
@@ -131,7 +131,18 @@ static int touch_mem(int *mem, int wss, int write_cycle)
         return sum;
 }
 
-
+static int pick_cpu(int last_cpu, int num_cpus)
+{
+        int cpu;
+        if (random() % 2 == 0)
+                return last_cpu; /* preemption */
+        else {
+                do {
+                        cpu = random() % num_cpus;
+                } while (cpu == last_cpu);
+                return cpu;
+        }
+}
 
 static void do_random_experiment(FILE* outfile,
                                  int num_cpus, int wss,
@@ -162,7 +173,7 @@ static void do_random_experiment(FILE* outfile,
                sample_count >= migration_counter) {
 
                 delay = sleep_min + random() % (sleep_max - sleep_min + 1);
-                next_cpu = random() % num_cpus;
+                next_cpu = pick_cpu(last_cpu, num_cpus);
 
                 if (sample_count)
                         show = (next_cpu == last_cpu && sample_count >= preempt_counter) ||