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>

3 files changed, 149 insertions, 0 deletions

diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
index 32a010d5edb9..43dc27997730 100644
--- a/arch/mips/Kconfig.debug
+++ b/arch/mips/Kconfig.debug
@@ -121,4 +121,11 @@ config DEBUG_ZBOOT
           to reduce the kernel image size and speed up the booting procedure a
           little.
 
+config SPINLOCK_TEST
+        bool "Enable spinlock timing tests in debugfs"
+        depends on DEBUG_FS
+        default n
+        help
+          Add several files to the debugfs to test spinlock speed.
+
 endmenu
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 9326af5186fe..ef20957ca14b 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -93,6 +93,7 @@ obj-$(CONFIG_GPIO_TXX9)		+= gpio_txx9.o
 
 obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
 obj-$(CONFIG_EARLY_PRINTK)      += early_printk.o
+obj-$(CONFIG_SPINLOCK_TEST)     += spinlock_test.o
 
 CFLAGS_cpu-bugs64.o     = $(shell if $(CC) $(KBUILD_CFLAGS) -Wa,-mdaddi -c -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo "-DHAVE_AS_SET_DADDI"; fi)
 
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);