s390/vtime: limit MT scaling value updates

[deliverable/linux.git] / arch / s390 / kernel / vtime.c

diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index e53d3595a7c8c1a54400d5fb3e984004cd864219..b9ce650e9e992065aa611f5bc654f59b5b8bf40f 100644 (file)
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -28,6 +28,7 @@ static atomic64_t virt_timer_elapsed;
 static DEFINE_PER_CPU(u64, mt_cycles[32]);
 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);
 
 static inline u64 get_vtimer(void)
 {
@@ -85,7 +86,8 @@ static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
        S390_lowcore.steal_timer += S390_lowcore.last_update_clock - clock;
 
        /* Do MT utilization calculation */
-       if (smp_cpu_mtid) {
+       if (smp_cpu_mtid &&
+           time_after64(jiffies_64, __this_cpu_read(mt_scaling_jiffies))) {
                u64 cycles_new[32], *cycles_old;
                u64 delta, mult, div;
 
@@ -105,6 +107,7 @@ static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
                                       sizeof(u64) * (smp_cpu_mtid + 1));
                        }
                }
+               __this_cpu_write(mt_scaling_jiffies, jiffies_64);
        }
 
        user = S390_lowcore.user_timer - ti->user_timer;
@@ -376,4 +379,11 @@ void vtime_init(void)
 {
        /* set initial cpu timer */
        set_vtimer(VTIMER_MAX_SLICE);
+       /* Setup initial MT scaling values */
+       if (smp_cpu_mtid) {
+               __this_cpu_write(mt_scaling_jiffies, jiffies);
+               __this_cpu_write(mt_scaling_mult, 1);
+               __this_cpu_write(mt_scaling_div, 1);
+               stcctm5(smp_cpu_mtid + 1, this_cpu_ptr(mt_cycles));
+       }
 }