From 3c5d92a0cfb5103c0d5ab74d4ae6373d3af38148 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Tue, 29 Sep 2009 14:25:16 +0200 Subject: 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 LKML-Reference: <20090929122533.402715150@de.ibm.com> Signed-off-by: Thomas Gleixner --- arch/s390/include/asm/cputime.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch/s390/include') diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h index 24b1244aadb..95f3561517c 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 */ -- cgit v1.2.3-70-g09d2