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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2009-09-29 14:25:16 +0200
committerThomas Gleixner <tglx@linutronix.de>2009-11-05 07:53:53 +0100
commit3c5d92a0cfb5103c0d5ab74d4ae6373d3af38148 (patch)
treec8b50351568601428b6f9396ebfdd65e486b3097 /arch/s390/include
parenteed3b9cf3fe3fcc7a50238dfcab63a63914e8f42 (diff)
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>
Diffstat (limited to 'arch/s390/include')
-rw-r--r--arch/s390/include/asm/cputime.h8
1 files changed, 8 insertions, 0 deletions
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 */