Commit bba90760 authored by David Daney's avatar David Daney Committed by Ralf Baechle
Browse files

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: default avatarDavid Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/969/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent 500c2e1f

arch/mips/Kconfig.debug

+7 −0
Original line number Diff line number Diff line
@@ -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

arch/mips/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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)

arch/mips/kernel/spinlock_test.c

0 → 100644
+141 −0
Original line number Diff line number Diff line 
#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);

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