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Commit 72d38b19 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390/vtime: correct scaled cputime of partially idle CPUs 



The calculation for the SMT scaling factor for a hardware thread
which has been partially idle needs to disregard the cycles spent
by the other threads of the core while the thread is idle.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent adc0b7fb

arch/s390/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -176,6 +176,7 @@ int main(void) 
	DEFINE(__LC_PASTE, offsetof(struct _lowcore, paste));

	DEFINE(__LC_FP_CREG_SAVE_AREA, offsetof(struct _lowcore, fpt_creg_save_area));

	DEFINE(__LC_LAST_BREAK, offsetof(struct _lowcore, breaking_event_addr));

	DEFINE(__LC_PERCPU_OFFSET, offsetof(struct _lowcore, percpu_offset));

	DEFINE(__LC_VDSO_PER_CPU, offsetof(struct _lowcore, vdso_per_cpu_data));

	DEFINE(__LC_GMAP, offsetof(struct _lowcore, gmap));

	DEFINE(__LC_PGM_TDB, offsetof(struct _lowcore, pgm_tdb));

arch/s390/kernel/entry.S

+29 −1
Original line number Diff line number Diff line
@@ -733,6 +733,14 @@ ENTRY(psw_idle) 
	stg	%r3,__SF_EMPTY(%r15)

	larl	%r1,.Lpsw_idle_lpsw+4

	stg	%r1,__SF_EMPTY+8(%r15)

#ifdef CONFIG_SMP

	larl	%r1,smp_cpu_mtid

	llgf	%r1,0(%r1)

	ltgr	%r1,%r1

	jz	.Lpsw_idle_stcctm

	.insn	rsy,0xeb0000000017,%r1,5,__SF_EMPTY+16(%r15)

.Lpsw_idle_stcctm:

#endif

	STCK	__CLOCK_IDLE_ENTER(%r2)

	stpt	__TIMER_IDLE_ENTER(%r2)

.Lpsw_idle_lpsw:
@@ -1159,7 +1167,27 @@ cleanup_critical: 
	jhe	1f

	mvc	__CLOCK_IDLE_ENTER(8,%r2),__CLOCK_IDLE_EXIT(%r2)

	mvc	__TIMER_IDLE_ENTER(8,%r2),__TIMER_IDLE_EXIT(%r2)

1:	# account system time going idle

1:	# calculate idle cycles

#ifdef CONFIG_SMP

	clg	%r9,BASED(.Lcleanup_idle_insn)

	jl	3f

	larl	%r1,smp_cpu_mtid

	llgf	%r1,0(%r1)

	ltgr	%r1,%r1

	jz	3f

	.insn	rsy,0xeb0000000017,%r1,5,__SF_EMPTY+80(%r15)

	larl	%r3,mt_cycles

	ag	%r3,__LC_PERCPU_OFFSET

	la	%r4,__SF_EMPTY+16(%r15)

2:	lg	%r0,0(%r3)

	slg	%r0,0(%r4)

	alg	%r0,64(%r4)

	stg	%r0,0(%r3)

	la	%r3,8(%r3)

	la	%r4,8(%r4)

	brct	%r1,2b

#endif

3:	# account system time going idle

	lg	%r9,__LC_STEAL_TIMER

	alg	%r9,__CLOCK_IDLE_ENTER(%r2)

	slg	%r9,__LC_LAST_UPDATE_CLOCK

arch/s390/kernel/vtime.c

+37 −29
Original line number Diff line number Diff line
@@ -25,7 +25,7 @@ static DEFINE_SPINLOCK(virt_timer_lock); 
static atomic64_t virt_timer_current;

static atomic64_t virt_timer_elapsed;



static DEFINE_PER_CPU(u64, mt_cycles[32]);

DEFINE_PER_CPU(u64, mt_cycles[8]);

static DEFINE_PER_CPU(u64, mt_scaling_mult) = { 1 };

static DEFINE_PER_CPU(u64, mt_scaling_div) = { 1 };

static DEFINE_PER_CPU(u64, mt_scaling_jiffies);
@@ -60,6 +60,34 @@ static inline int virt_timer_forward(u64 elapsed) 
	return elapsed >= atomic64_read(&virt_timer_current);

}



static void update_mt_scaling(void)

{

	u64 cycles_new[8], *cycles_old;

	u64 delta, fac, mult, div;

	int i;



	stcctm5(smp_cpu_mtid + 1, cycles_new);

	cycles_old = this_cpu_ptr(mt_cycles);

	fac = 1;

	mult = div = 0;

	for (i = 0; i <= smp_cpu_mtid; i++) {

		delta = cycles_new[i] - cycles_old[i];

		div += delta;

		mult *= i + 1;

		mult += delta * fac;

		fac *= i + 1;

	}

	div *= fac;

	if (div > 0) {

		/* Update scaling factor */

		__this_cpu_write(mt_scaling_mult, mult);

		__this_cpu_write(mt_scaling_div, div);

		memcpy(cycles_old, cycles_new,

		       sizeof(u64) * (smp_cpu_mtid + 1));

	}

	__this_cpu_write(mt_scaling_jiffies, jiffies_64);

}



/*

 * Update process times based on virtual cpu times stored by entry.S

 * to the lowcore fields user_timer, system_timer & steal_clock.
@@ -69,7 +97,6 @@ static int do_account_vtime(struct task_struct *tsk, int hardirq_offset) 
	struct thread_info *ti = task_thread_info(tsk);

	u64 timer, clock, user, system, steal;

	u64 user_scaled, system_scaled;

	int i;



	timer = S390_lowcore.last_update_timer;

	clock = S390_lowcore.last_update_clock;
@@ -85,34 +112,10 @@ static int do_account_vtime(struct task_struct *tsk, int hardirq_offset) 
	S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

	S390_lowcore.steal_timer += S390_lowcore.last_update_clock - clock;



	/* Do MT utilization calculation */

	/* Update MT utilization calculation */

	if (smp_cpu_mtid &&

	    time_after64(jiffies_64, __this_cpu_read(mt_scaling_jiffies))) {

		u64 cycles_new[32], *cycles_old;

		u64 delta, fac, mult, div;



		cycles_old = this_cpu_ptr(mt_cycles);

		if (stcctm5(smp_cpu_mtid + 1, cycles_new) < 2) {

			fac = 1;

			mult = div = 0;

			for (i = 0; i <= smp_cpu_mtid; i++) {

				delta = cycles_new[i] - cycles_old[i];

				div += delta;

				mult *= i + 1;

				mult += delta * fac;

				fac *= i + 1;

			}

			div *= fac;

			if (div > 0) {

				/* Update scaling factor */

				__this_cpu_write(mt_scaling_mult, mult);

				__this_cpu_write(mt_scaling_div, div);

				memcpy(cycles_old, cycles_new,

				       sizeof(u64) * (smp_cpu_mtid + 1));

			}

		}

		__this_cpu_write(mt_scaling_jiffies, jiffies_64);

	}

	    time_after64(jiffies_64, this_cpu_read(mt_scaling_jiffies)))

		update_mt_scaling();



	user = S390_lowcore.user_timer - ti->user_timer;

	S390_lowcore.steal_timer -= user;
@@ -181,6 +184,11 @@ void vtime_account_irq_enter(struct task_struct *tsk) 
	S390_lowcore.last_update_timer = get_vtimer();

	S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;



	/* Update MT utilization calculation */

	if (smp_cpu_mtid &&

	    time_after64(jiffies_64, this_cpu_read(mt_scaling_jiffies)))

		update_mt_scaling();



	system = S390_lowcore.system_timer - ti->system_timer;

	S390_lowcore.steal_timer -= system;

	ti->system_timer = S390_lowcore.system_timer;