+/* test-cmpxchg-nolock.c
+ *
+ * Compare local cmpxchg with irq disable / enable.
+ */
+
+
+#include <linux/jiffies.h>
+#include <linux/compiler.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/calc64.h>
+#include <asm/timex.h>
+#include <asm/system.h>
+
+#define NR_LOOPS 20000
+
+int test_val;
+
+static void do_test_cmpxchg(void)
+{
+ int ret;
+ long flags;
+ unsigned int i;
+ cycles_t time1, time2, time;
+ long rem;
+
+ local_irq_save(flags);
+ preempt_disable();
+ time1 = get_cycles();
+ for (i = 0; i < NR_LOOPS; i++) {
+ ret = cmpxchg_local(&test_val, 0, 0);
+ }
+ time2 = get_cycles();
+ local_irq_restore(flags);
+ preempt_enable();
+ time = time2 - time1;
+
+ printk(KERN_ALERT "test results: time for non locked cmpxchg\n");
+ printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS);
+ printk(KERN_ALERT "total time: %llu\n", time);
+ time = div_long_long_rem(time, NR_LOOPS, &rem);
+ printk(KERN_ALERT "-> non locked cmpxchg takes %llu cycles\n", time);
+ printk(KERN_ALERT "test end\n");
+}
+
+/*
+ * This test will have a higher standard deviation due to incoming interrupts.
+ */
+static void do_test_enable_int(void)
+{
+ long flags;
+ unsigned int i;
+ cycles_t time1, time2, time;
+ long rem;
+
+ local_irq_save(flags);
+ preempt_disable();
+ time1 = get_cycles();
+ for (i = 0; i < NR_LOOPS; i++) {
+ local_irq_restore(flags);
+ }
+ time2 = get_cycles();
+ local_irq_restore(flags);
+ preempt_enable();
+ time = time2 - time1;
+
+ printk(KERN_ALERT "test results: time for enabling interrupts (STI)\n");
+ printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS);
+ printk(KERN_ALERT "total time: %llu\n", time);
+ time = div_long_long_rem(time, NR_LOOPS, &rem);
+ printk(KERN_ALERT "-> enabling interrupts (STI) takes %llu cycles\n",
+ time);
+ printk(KERN_ALERT "test end\n");
+}
+
+static void do_test_disable_int(void)
+{
+ unsigned long flags, flags2;
+ unsigned int i;
+ cycles_t time1, time2, time;
+ long rem;
+
+ local_irq_save(flags);
+ preempt_disable();
+ time1 = get_cycles();
+ for ( i = 0; i < NR_LOOPS; i++) {
+ local_irq_save(flags2);
+ }
+ time2 = get_cycles();
+ local_irq_restore(flags);
+ preempt_enable();
+ time = time2 - time1;
+
+ printk(KERN_ALERT "test results: time for disabling interrupts (CLI)\n");
+ printk(KERN_ALERT "number of loops: %d\n", NR_LOOPS);
+ printk(KERN_ALERT "total time: %llu\n", time);
+ time = div_long_long_rem(time, NR_LOOPS, &rem);
+ printk(KERN_ALERT "-> disabling interrupts (CTI) takes %llu cycles\n",
+ time);
+ printk(KERN_ALERT "test end\n");
+}
+
+
+
+static int ltt_test_init(void)
+{
+ printk(KERN_ALERT "test init\n");
+
+ do_test_cmpxchg();
+ do_test_enable_int();
+ do_test_disable_int();
+ return -EAGAIN; /* Fail will directly unload the module */
+}
+
+static void ltt_test_exit(void)
+{
+ printk(KERN_ALERT "test exit\n");
+}
+
+module_init(ltt_test_init)
+module_exit(ltt_test_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Cmpxchg vs int Test");
+