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author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2009-06-22 12:08:20 +0200 |
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committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2009-06-22 12:08:23 +0200 |
commit | e98bbaafcd1c47d30f3245517fb585f1aaaca4db (patch) | |
tree | 8c8c88910db0197acc92bf1ddef999816f1a778b | |
parent | 4f0076f77fb64889d4e5e425b63333e5764b446d (diff) | |
download | kernel_goldelico_gta04-e98bbaafcd1c47d30f3245517fb585f1aaaca4db.zip kernel_goldelico_gta04-e98bbaafcd1c47d30f3245517fb585f1aaaca4db.tar.gz kernel_goldelico_gta04-e98bbaafcd1c47d30f3245517fb585f1aaaca4db.tar.bz2 |
[S390] lockless idle time accounting
Replace the spinlock used in the idle time accounting with a sequence
counter mechanism analog to seqlock.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
-rw-r--r-- | arch/s390/include/asm/cputime.h | 2 | ||||
-rw-r--r-- | arch/s390/kernel/smp.c | 28 | ||||
-rw-r--r-- | arch/s390/kernel/vtime.c | 22 |
3 files changed, 35 insertions, 17 deletions
diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h index ec917d4..7a3817a 100644 --- a/arch/s390/include/asm/cputime.h +++ b/arch/s390/include/asm/cputime.h @@ -178,7 +178,7 @@ cputime64_to_clock_t(cputime64_t cputime) } struct s390_idle_data { - spinlock_t lock; + unsigned int sequence; unsigned long long idle_count; unsigned long long idle_enter; unsigned long long idle_time; diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index fd8e311..2270730 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -856,13 +856,20 @@ static ssize_t show_idle_count(struct sys_device *dev, { struct s390_idle_data *idle; unsigned long long idle_count; + unsigned int sequence; idle = &per_cpu(s390_idle, dev->id); - spin_lock(&idle->lock); +repeat: + sequence = idle->sequence; + smp_rmb(); + if (sequence & 1) + goto repeat; idle_count = idle->idle_count; if (idle->idle_enter) idle_count++; - spin_unlock(&idle->lock); + smp_rmb(); + if (idle->sequence != sequence) + goto repeat; return sprintf(buf, "%llu\n", idle_count); } static SYSDEV_ATTR(idle_count, 0444, show_idle_count, NULL); @@ -872,15 +879,22 @@ static ssize_t show_idle_time(struct sys_device *dev, { struct s390_idle_data *idle; unsigned long long now, idle_time, idle_enter; + unsigned int sequence; idle = &per_cpu(s390_idle, dev->id); - spin_lock(&idle->lock); now = get_clock(); +repeat: + sequence = idle->sequence; + smp_rmb(); + if (sequence & 1) + goto repeat; idle_time = idle->idle_time; idle_enter = idle->idle_enter; if (idle_enter != 0ULL && idle_enter < now) idle_time += now - idle_enter; - spin_unlock(&idle->lock); + smp_rmb(); + if (idle->sequence != sequence) + goto repeat; return sprintf(buf, "%llu\n", idle_time >> 12); } static SYSDEV_ATTR(idle_time_us, 0444, show_idle_time, NULL); @@ -908,11 +922,7 @@ static int __cpuinit smp_cpu_notify(struct notifier_block *self, case CPU_ONLINE: case CPU_ONLINE_FROZEN: idle = &per_cpu(s390_idle, cpu); - spin_lock_irq(&idle->lock); - idle->idle_enter = 0; - idle->idle_time = 0; - idle->idle_count = 0; - spin_unlock_irq(&idle->lock); + memset(idle, 0, sizeof(struct s390_idle_data)); if (sysfs_create_group(&s->kobj, &cpu_online_attr_group)) return NOTIFY_BAD; break; diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c index ade17e7..c41bb0d 100644 --- a/arch/s390/kernel/vtime.c +++ b/arch/s390/kernel/vtime.c @@ -27,9 +27,7 @@ static DEFINE_PER_CPU(struct vtimer_queue, virt_cpu_timer); -DEFINE_PER_CPU(struct s390_idle_data, s390_idle) = { - .lock = __SPIN_LOCK_UNLOCKED(s390_idle.lock) -}; +DEFINE_PER_CPU(struct s390_idle_data, s390_idle); static inline __u64 get_vtimer(void) { @@ -151,11 +149,13 @@ void vtime_start_cpu(void) vq->elapsed -= vq->idle - S390_lowcore.async_enter_timer; } - spin_lock(&idle->lock); + idle->sequence++; + smp_wmb(); idle->idle_time += idle_time; idle->idle_enter = 0ULL; idle->idle_count++; - spin_unlock(&idle->lock); + smp_wmb(); + idle->sequence++; } void vtime_stop_cpu(void) @@ -242,15 +242,23 @@ cputime64_t s390_get_idle_time(int cpu) { struct s390_idle_data *idle; unsigned long long now, idle_time, idle_enter; + unsigned int sequence; idle = &per_cpu(s390_idle, cpu); - spin_lock(&idle->lock); + now = get_clock(); +repeat: + sequence = idle->sequence; + smp_rmb(); + if (sequence & 1) + goto repeat; idle_time = 0; idle_enter = idle->idle_enter; if (idle_enter != 0ULL && idle_enter < now) idle_time = now - idle_enter; - spin_unlock(&idle->lock); + smp_rmb(); + if (idle->sequence != sequence) + goto repeat; return idle_time; } |