From 6378724095a1b00a21a543318ae115a185fb0884 Mon Sep 17 00:00:00 2001
From: compudj <compudj@04897980-b3bd-0310-b5e0-8ef037075253>
Date: Tue, 20 Mar 2007 20:36:29 +0000
Subject: [PATCH] add test-tsc

git-svn-id: http://ltt.polymtl.ca/svn@2446 04897980-b3bd-0310-b5e0-8ef037075253
---
 tests/kernel/Makefile        |   1 +
 tests/kernel/test-tsc-sync.c |   2 +-
 tests/kernel/test-tsc.c      | 107 +++++++++++++++++++++++++++++++++++
 3 files changed, 109 insertions(+), 1 deletion(-)
 create mode 100644 tests/kernel/test-tsc.c

diff --git a/tests/kernel/Makefile b/tests/kernel/Makefile
index 69d5ff2a..01259f55 100644
--- a/tests/kernel/Makefile
+++ b/tests/kernel/Makefile
@@ -12,6 +12,7 @@ ifneq ($(CONFIG_LTT),)
 endif
 #	obj-m += test-async-tsc.o
 	obj-m += test-tsc-sync.o
+	obj-m += test-tsc.o
 #	obj-m += test-hpet.o
 	#obj-m += test-debugfs.o
 #	obj-m += test-mod.o
diff --git a/tests/kernel/test-tsc-sync.c b/tests/kernel/test-tsc-sync.c
index 200839ab..14cd008b 100644
--- a/tests/kernel/test-tsc-sync.c
+++ b/tests/kernel/test-tsc-sync.c
@@ -24,7 +24,7 @@ static void test_each(void *info)
 	atomic_dec(&kernel_threads_to_run);
 	while(atomic_read(&kernel_threads_to_run))
 		cpu_relax();
-	__get_cpu_var(count) = get_cycles();
+	__get_cpu_var(count) = get_cycles_sync();
 	local_irq_restore(flags);
 }
 
diff --git a/tests/kernel/test-tsc.c b/tests/kernel/test-tsc.c
new file mode 100644
index 00000000..8a3991f0
--- /dev/null
+++ b/tests/kernel/test-tsc.c
@@ -0,0 +1,107 @@
+/* test-tsc.c
+ *
+ * Test TSC synchronization
+ */
+
+
+#include <linux/module.h>
+#include <linux/timer.h>
+#include <asm/timex.h>
+#include <linux/jiffies.h>
+#include <linux/cpu.h>
+#include <linux/kthread.h>
+
+#define MAX_CYCLES_DELTA 1000ULL
+
+static DEFINE_PER_CPU(cycles_t, tsc_count) = 0;
+
+static atomic_t wait_sync;
+static atomic_t wait_end_sync;
+
+/* Mark it noinline so we make sure it is not unrolled.
+ * Wait until value is reached. */
+static noinline void tsc_barrier(int value)
+{
+	sync_core();
+	atomic_dec(&wait_sync);
+	do {
+		barrier();
+	} while(unlikely(atomic_read(&wait_sync) > value));
+	__get_cpu_var(tsc_count) = get_cycles_sync();
+}
+
+/* worker thread called on each CPU.
+ * First wait with interrupts enabled, then wait with interrupt disabled,
+ * for precision. We are already bound to one CPU. */
+static void test_sync(void *arg)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	tsc_barrier(2);	/* Make sure the instructions are in I-CACHE */
+	tsc_barrier(0);
+	atomic_dec(&wait_end_sync);
+	do {
+		barrier();
+	} while(unlikely(atomic_read(&wait_end_sync)));
+	local_irq_restore(flags);
+}
+
+/* Do loops (making sure no unexpected event changes the timing), keep the
+ * best one. The result of each loop is the highest tsc delta between the
+ * master CPU and the slaves. */
+static int test_synchronization(void)
+{
+	int cpu, master;
+	cycles_t max_diff = 0, diff, best_loop, worse_loop = 0;
+	int i;
+
+	preempt_disable();
+	master = smp_processor_id();
+	for_each_online_cpu(cpu) {
+		if (master == cpu)
+			continue;
+		best_loop = ULLONG_MAX;
+		for (i = 0; i < 10; i++) {
+			/* Each CPU (master and slave) must decrement the
+			 * wait_sync value twice (one for priming in cache) */
+			atomic_set(&wait_sync, 4);
+			atomic_set(&wait_end_sync, 2);
+			smp_call_function_single(cpu, test_sync, NULL, 1, 0);
+			test_sync(NULL);
+			diff = abs(per_cpu(tsc_count, cpu)
+				- per_cpu(tsc_count, master));
+			best_loop = min(best_loop, diff);
+			worse_loop = max(worse_loop, diff);
+		}
+		max_diff = max(best_loop, max_diff);
+	}
+	preempt_enable();
+	if (max_diff >= MAX_CYCLES_DELTA) {
+		printk("Synchronization tsc : %llu cycles delta is over "
+			"threshold %llu\n", max_diff, MAX_CYCLES_DELTA);
+		printk("Synchronization tsc (worse loop) : %llu cycles delta\n",
+			worse_loop);
+	}
+	return max_diff < MAX_CYCLES_DELTA;
+}
+
+static int __init test_init(void)
+{
+	int ret;
+
+	ret = test_synchronization();
+	return 0;
+}
+
+static void __exit test_exit(void)
+{
+}
+
+module_init(test_init);
+module_exit(test_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("sync tsc test");
+
-- 
2.34.1