MIPS: Crazy spinlock speed test.

This is just a test program for raw_spinlocks.  The main reason I
wrote it is to validate my spinlock changes that I sent in a previous
patch.

To use it enable CONFIG_DEBUG_FS and CONFIG_SPINLOCK_TEST then at run
time do:

# mount -t debugfs none /sys/kernel/debug/
# cat /sys/kernel/debug/mips/spin_single
# cat /sys/kernel/debug/mips/spin_multi

On my 600MHz octeon cn5860 (16 CPUs) I get

		spin_single	spin_multi
base		106885		247941
spinlock_patch	75194		219465

This shows that for uncontended locks the spinlock patch gives 41%
improvement and for contended locks 12% improvement (1/time).

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/969/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 141 insertions, 0 deletions

diff --git a/arch/mips/kernel/spinlock_test.c b/arch/mips/kernel/spinlock_test.c
new file mode 100644
index 000000000000..da61134dfc53
--- /dev/null
+++ b/arch/mips/kernel/spinlock_test.c
@@ -0,0 +1,141 @@
+#include <linux/init.h>
+#include <linux/kthread.h>
+#include <linux/hrtimer.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+
+
+static int ss_get(void *data, u64 *val)
+{
+	ktime_t start, finish;
+	int loops;
+	int cont;
+	DEFINE_RAW_SPINLOCK(ss_spin);
+
+	loops = 1000000;
+	cont = 1;
+
+	start = ktime_get();
+
+	while (cont) {
+		raw_spin_lock(&ss_spin);
+		loops--;
+		if (loops == 0)
+			cont = 0;
+		raw_spin_unlock(&ss_spin);
+	}
+
+	finish = ktime_get();
+
+	*val = ktime_us_delta(finish, start);
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_ss, ss_get, NULL, "%llu\n");
+
+
+
+struct spin_multi_state {
+	raw_spinlock_t lock;
+	atomic_t start_wait;
+	atomic_t enter_wait;
+	atomic_t exit_wait;
+	int loops;
+};
+
+struct spin_multi_per_thread {
+	struct spin_multi_state *state;
+	ktime_t start;
+};
+
+static int multi_other(void *data)
+{
+	int loops;
+	int cont;
+	struct spin_multi_per_thread *pt = data;
+	struct spin_multi_state *s = pt->state;
+
+	loops = s->loops;
+	cont = 1;
+
+	atomic_dec(&s->enter_wait);
+
+	while (atomic_read(&s->enter_wait))
+		; /* spin */
+
+	pt->start = ktime_get();
+
+	atomic_dec(&s->start_wait);
+
+	while (atomic_read(&s->start_wait))
+		; /* spin */
+
+	while (cont) {
+		raw_spin_lock(&s->lock);
+		loops--;
+		if (loops == 0)
+			cont = 0;
+		raw_spin_unlock(&s->lock);
+	}
+
+	atomic_dec(&s->exit_wait);
+	while (atomic_read(&s->exit_wait))
+		; /* spin */
+	return 0;
+}
+
+static int multi_get(void *data, u64 *val)
+{
+	ktime_t finish;
+	struct spin_multi_state ms;
+	struct spin_multi_per_thread t1, t2;
+
+	ms.lock = __RAW_SPIN_LOCK_UNLOCKED("multi_get");
+	ms.loops = 1000000;
+
+	atomic_set(&ms.start_wait, 2);
+	atomic_set(&ms.enter_wait, 2);
+	atomic_set(&ms.exit_wait, 2);
+	t1.state = &ms;
+	t2.state = &ms;
+
+	kthread_run(multi_other, &t2, "multi_get");
+
+	multi_other(&t1);
+
+	finish = ktime_get();
+
+	*val = ktime_us_delta(finish, t1.start);
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_multi, multi_get, NULL, "%llu\n");
+
+
+extern struct dentry *mips_debugfs_dir;
+static int __init spinlock_test(void)
+{
+	struct dentry *d;
+
+	if (!mips_debugfs_dir)
+		return -ENODEV;
+
+	d = debugfs_create_file("spin_single", S_IRUGO,
+				mips_debugfs_dir, NULL,
+				&fops_ss);
+	if (!d)
+		return -ENOMEM;
+
+	d = debugfs_create_file("spin_multi", S_IRUGO,
+				mips_debugfs_dir, NULL,
+				&fops_multi);
+	if (!d)
+		return -ENOMEM;
+
+	return 0;
+}
+device_initcall(spinlock_test);