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 --- drivers/s390/cio/cio.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/s390') diff --git a/drivers/s390/cio/cio.c b/drivers/s390/cio/cio.c index 138124fcfcad..126f240715a4 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(); -- cgit v1.2.3-59-g8ed1b