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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2015-09-18 17:41:36 +0300
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2015-09-30 17:22:38 +0300
commit72d38b19781de457def0a62dfaa50134fc6e15f0 (patch)
tree142bbab792f048ffbad3980f11150a19f47c4604 /arch/s390/kernel/vtime.c
parentadc0b7fbf6fe9967505c0254d9535ec7288186ae (diff)
downloadlinux-72d38b19781de457def0a62dfaa50134fc6e15f0.tar.xz
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>
Diffstat (limited to 'arch/s390/kernel/vtime.c')
-rw-r--r--arch/s390/kernel/vtime.c66
1 files changed, 37 insertions, 29 deletions
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index c8653435c70d..dafc44f519c3 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -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;