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Commit 6f430924 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

[PATCH] improve precision of idle time detection. 



Increase the precision of the idle time calculation that is exported
to user space via /sys/devices/system/cpu/cpu<x>/idle_time_us

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent aa5e97ce

arch/s390/include/asm/cpu.h

+1 −2
Original line number Diff line number Diff line
@@ -14,7 +14,6 @@ 


struct s390_idle_data {

	spinlock_t lock;

	unsigned int in_idle;

	unsigned long long idle_count;

	unsigned long long idle_enter;

	unsigned long long idle_time;
@@ -26,7 +25,7 @@ void s390_idle_leave(void); 


static inline void s390_idle_check(void)

{

	if ((&__get_cpu_var(s390_idle))->in_idle)

	if ((&__get_cpu_var(s390_idle))->idle_enter != 0ULL)

		s390_idle_leave();

}

arch/s390/kernel/process.c

+45 −22
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ 
#include <linux/utsname.h>

#include <linux/tick.h>

#include <linux/elfcore.h>

#include <linux/kernel_stat.h>

#include <asm/uaccess.h>

#include <asm/pgtable.h>

#include <asm/system.h>
@@ -79,30 +80,19 @@ DEFINE_PER_CPU(struct s390_idle_data, s390_idle) = { 
	.lock = __SPIN_LOCK_UNLOCKED(s390_idle.lock)

};



static int s390_idle_enter(void)

void s390_idle_leave(void)

{

	struct s390_idle_data *idle;

	unsigned long long idle_time;



	idle = &__get_cpu_var(s390_idle);

	idle_time = S390_lowcore.int_clock - idle->idle_enter;

	spin_lock(&idle->lock);

	idle->idle_time += idle_time;

	idle->idle_enter = 0ULL;

	idle->idle_count++;

	idle->in_idle = 1;

	idle->idle_enter = get_clock();

	spin_unlock(&idle->lock);

	vtime_stop_cpu_timer();

	return NOTIFY_OK;

}



void s390_idle_leave(void)

{

	struct s390_idle_data *idle;



	vtime_start_cpu_timer();

	idle = &__get_cpu_var(s390_idle);

	spin_lock(&idle->lock);

	idle->idle_time += get_clock() - idle->idle_enter;

	idle->in_idle = 0;

	spin_unlock(&idle->lock);

}



extern void s390_handle_mcck(void);
@@ -111,16 +101,16 @@ extern void s390_handle_mcck(void); 
 */

static void default_idle(void)

{

	struct s390_idle_data *idle = &__get_cpu_var(s390_idle);

	unsigned long addr;

	psw_t psw;



	/* CPU is going idle. */

	local_irq_disable();

	if (need_resched()) {

		local_irq_enable();

		return;

	}

	if (s390_idle_enter() == NOTIFY_BAD) {

		local_irq_enable();

		return;

	}

#ifdef CONFIG_HOTPLUG_CPU

	if (cpu_is_offline(smp_processor_id())) {

		preempt_enable_no_resched();
@@ -138,9 +128,42 @@ static void default_idle(void) 
	trace_hardirqs_on();

	/* Don't trace preempt off for idle. */

	stop_critical_timings();

	vtime_stop_cpu_timer();



	/*

	 * The inline assembly is equivalent to

	 *	idle->idle_enter = get_clock();

	 *	__load_psw_mask(psw_kernel_bits | PSW_MASK_WAIT |

	 *			   PSW_MASK_IO | PSW_MASK_EXT);

	 * The difference is that the inline assembly makes sure that

	 * the stck instruction is right before the lpsw instruction.

	 * This is done to increase the precision.

	 */



	/* Wait for external, I/O or machine check interrupt. */

	__load_psw_mask(psw_kernel_bits | PSW_MASK_WAIT |

			PSW_MASK_IO | PSW_MASK_EXT);

	psw.mask = psw_kernel_bits|PSW_MASK_WAIT|PSW_MASK_IO|PSW_MASK_EXT;

#ifndef __s390x__

	asm volatile(

		"	basr	%0,0\n"

		"0:	ahi	%0,1f-0b\n"

		"	st	%0,4(%2)\n"

		"	stck	0(%3)\n"

		"	lpsw	0(%2)\n"

		"1:"

		: "=&d" (addr), "=m" (idle->idle_enter)

		: "a" (&psw), "a" (&idle->idle_enter), "m" (psw)

		: "memory", "cc");

#else /* __s390x__ */

	asm volatile(

		"	larl	%0,1f\n"

		"	stg	%0,8(%2)\n"

		"	stck	0(%3)\n"

		"	lpswe	0(%2)\n"

		"1:"

		: "=&d" (addr), "=m" (idle->idle_enter)

		: "a" (&psw), "a" (&idle->idle_enter), "m" (psw)

		: "memory", "cc");

#endif /* __s390x__ */

	start_critical_timings();

}

arch/s390/kernel/smp.c

+13 −12
Original line number Diff line number Diff line
@@ -851,9 +851,11 @@ static ssize_t show_idle_count(struct sys_device *dev, 
	unsigned long long idle_count;



	idle = &per_cpu(s390_idle, dev->id);

	spin_lock_irq(&idle->lock);

	spin_lock(&idle->lock);

	idle_count = idle->idle_count;

	spin_unlock_irq(&idle->lock);

	if (idle->idle_enter)

		idle_count++;

	spin_unlock(&idle->lock);

	return sprintf(buf, "%llu\n", idle_count);

}

static SYSDEV_ATTR(idle_count, 0444, show_idle_count, NULL);
@@ -862,18 +864,17 @@ static ssize_t show_idle_time(struct sys_device *dev, 
				struct sysdev_attribute *attr, char *buf)

{

	struct s390_idle_data *idle;

	unsigned long long new_time;

	unsigned long long now, idle_time, idle_enter;



	idle = &per_cpu(s390_idle, dev->id);

	spin_lock_irq(&idle->lock);

	if (idle->in_idle) {

		new_time = get_clock();

		idle->idle_time += new_time - idle->idle_enter;

		idle->idle_enter = new_time;

	}

	new_time = idle->idle_time;

	spin_unlock_irq(&idle->lock);

	return sprintf(buf, "%llu\n", new_time >> 12);

	spin_lock(&idle->lock);

	now = get_clock();

	idle_time = idle->idle_time;

	idle_enter = idle->idle_enter;

	if (idle_enter != 0ULL && idle_enter < now)

		idle_time += now - idle_enter;

	spin_unlock(&idle->lock);

	return sprintf(buf, "%llu\n", idle_time >> 12);

}

static SYSDEV_ATTR(idle_time_us, 0444, show_idle_time, NULL);

arch/s390/kernel/vtime.c

+2 −1
Original line number Diff line number Diff line
@@ -112,6 +112,7 @@ EXPORT_SYMBOL_GPL(account_system_vtime); 


static inline void set_vtimer(__u64 expires)

{

	struct vtimer_queue *vq = &__get_cpu_var(virt_cpu_timer);

	__u64 timer;



	asm volatile ("  STPT %0\n"  /* Store current cpu timer value */
@@ -121,7 +122,7 @@ static inline void set_vtimer(__u64 expires) 
	S390_lowcore.last_update_timer = expires;



	/* store expire time for this CPU timer */

	__get_cpu_var(virt_cpu_timer).to_expire = expires;

	vq->to_expire = expires;

}



void vtime_start_cpu_timer(void)