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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2009-09-29 16:25:16 +0400
committerThomas Gleixner <tglx@linutronix.de>2009-11-05 09:53:53 +0300
commit3c5d92a0cfb5103c0d5ab74d4ae6373d3af38148 (patch)
treec8b50351568601428b6f9396ebfdd65e486b3097 /arch/s390
parenteed3b9cf3fe3fcc7a50238dfcab63a63914e8f42 (diff)
downloadlinux-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>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/include/asm/cputime.h8
-rw-r--r--arch/s390/kernel/s390_ext.c2
-rw-r--r--arch/s390/kernel/vtime.c2
3 files changed, 12 insertions, 0 deletions
diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h
index 24b1244aadb9..95f3561517c7 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 0de305b598ce..59618bcd99b7 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 c41bb0d416e1..b59a812a010e 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;