path: root/include
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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 /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 'include')
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 0482229c07d..8dc082194b2 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; }