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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2015-09-18 16:41:36 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2015-09-30 16:22:38 +0200
commit72d38b19781de457def0a62dfaa50134fc6e15f0 (patch)
tree142bbab792f048ffbad3980f11150a19f47c4604 /arch/s390
parentadc0b7fbf6fe9967505c0254d9535ec7288186ae (diff)
downloadlinux-72d38b19781de457def0a62dfaa50134fc6e15f0.tar.gz
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')
-rw-r--r--arch/s390/kernel/asm-offsets.c1
-rw-r--r--arch/s390/kernel/entry.S30
-rw-r--r--arch/s390/kernel/vtime.c66
3 files changed, 67 insertions, 30 deletions
diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index 48c9af7a7683..3aeeb1b562c0 100644
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -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));
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 09b039d7983d..582fe44ab07c 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -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
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;