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: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index c865343..dafc44f 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -25,7 +25,7 @@
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 @@
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 @@
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 @@
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 @@
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;