diff options
author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2009-09-29 12:25:16 (GMT) |
---|---|---|
committer | Thomas Gleixner <tglx@linutronix.de> | 2009-11-05 06:53:53 (GMT) |
commit | 3c5d92a0cfb5103c0d5ab74d4ae6373d3af38148 (patch) | |
tree | c8b50351568601428b6f9396ebfdd65e486b3097 | |
parent | eed3b9cf3fe3fcc7a50238dfcab63a63914e8f42 (diff) | |
download | linux-fsl-qoriq-3c5d92a0cfb5103c0d5ab74d4ae6373d3af38148.tar.xz |
nohz: Introduce arch_needs_cpu
Allow the architecture to request a normal jiffy tick when the system
goes idle and tick_nohz_stop_sched_tick is called . On s390 the hook is
used to prevent the system going fully idle if there has been an
interrupt other than a clock comparator interrupt since the last wakeup.
On s390 the HiperSockets response time for 1 connection ping-pong goes
down from 42 to 34 microseconds. The CPU cost decreases by 27%.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
LKML-Reference: <20090929122533.402715150@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r-- | arch/s390/include/asm/cputime.h | 8 | ||||
-rw-r--r-- | arch/s390/kernel/s390_ext.c | 2 | ||||
-rw-r--r-- | arch/s390/kernel/vtime.c | 2 | ||||
-rw-r--r-- | drivers/s390/cio/cio.c | 1 | ||||
-rw-r--r-- | include/linux/tick.h | 3 | ||||
-rw-r--r-- | kernel/time/tick-sched.c | 13 |
6 files changed, 24 insertions, 5 deletions
diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h index 24b1244..95f3561 100644 --- a/arch/s390/include/asm/cputime.h +++ b/arch/s390/include/asm/cputime.h @@ -183,6 +183,7 @@ struct s390_idle_data { unsigned long long idle_count; unsigned long long idle_enter; unsigned long long idle_time; + int nohz_delay; }; DECLARE_PER_CPU(struct s390_idle_data, s390_idle); @@ -198,4 +199,11 @@ static inline void s390_idle_check(void) vtime_start_cpu(); } +static inline int s390_nohz_delay(int cpu) +{ + return per_cpu(s390_idle, cpu).nohz_delay != 0; +} + +#define arch_needs_cpu(cpu) s390_nohz_delay(cpu) + #endif /* _S390_CPUTIME_H */ diff --git a/arch/s390/kernel/s390_ext.c b/arch/s390/kernel/s390_ext.c index 0de305b..59618bc 100644 --- a/arch/s390/kernel/s390_ext.c +++ b/arch/s390/kernel/s390_ext.c @@ -126,6 +126,8 @@ void __irq_entry do_extint(struct pt_regs *regs, unsigned short code) /* Serve timer interrupts first. */ clock_comparator_work(); kstat_cpu(smp_processor_id()).irqs[EXTERNAL_INTERRUPT]++; + if (code != 0x1004) + __get_cpu_var(s390_idle).nohz_delay = 1; index = ext_hash(code); for (p = ext_int_hash[index]; p; p = p->next) { if (likely(p->code == code)) diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c index c41bb0d..b59a812 100644 --- a/arch/s390/kernel/vtime.c +++ b/arch/s390/kernel/vtime.c @@ -167,6 +167,8 @@ void vtime_stop_cpu(void) /* Wait for external, I/O or machine check interrupt. */ psw.mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_IO | PSW_MASK_EXT; + idle->nohz_delay = 0; + /* Check if the CPU timer needs to be reprogrammed. */ if (vq->do_spt) { __u64 vmax = VTIMER_MAX_SLICE; diff --git a/drivers/s390/cio/cio.c b/drivers/s390/cio/cio.c index 138124f..126f240 100644 --- a/drivers/s390/cio/cio.c +++ b/drivers/s390/cio/cio.c @@ -618,6 +618,7 @@ void __irq_entry do_IRQ(struct pt_regs *regs) old_regs = set_irq_regs(regs); s390_idle_check(); irq_enter(); + __get_cpu_var(s390_idle).nohz_delay = 1; if (S390_lowcore.int_clock >= S390_lowcore.clock_comparator) /* Serve timer interrupts first. */ clock_comparator_work(); diff --git a/include/linux/tick.h b/include/linux/tick.h index 0482229..8dc0821 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -98,6 +98,9 @@ extern int tick_check_oneshot_change(int allow_nohz); extern struct tick_sched *tick_get_tick_sched(int cpu); extern void tick_check_idle(int cpu); extern int tick_oneshot_mode_active(void); +# ifndef arch_needs_cpu +# define arch_needs_cpu(cpu) (0) +# endif # else static inline void tick_clock_notify(void) { } static inline int tick_check_oneshot_change(int allow_nohz) { return 0; } diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 7378e2c..3840f6d 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -264,12 +264,15 @@ void tick_nohz_stop_sched_tick(int inidle) last_jiffies = jiffies; } while (read_seqretry(&xtime_lock, seq)); - /* Get the next timer wheel timer */ - next_jiffies = get_next_timer_interrupt(last_jiffies); - delta_jiffies = next_jiffies - last_jiffies; - - if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu)) + if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) || + arch_needs_cpu(cpu)) { + next_jiffies = last_jiffies + 1; delta_jiffies = 1; + } else { + /* Get the next timer wheel timer */ + next_jiffies = get_next_timer_interrupt(last_jiffies); + delta_jiffies = next_jiffies - last_jiffies; + } /* * Do not stop the tick, if we are only one off * or if the cpu is required for rcu |