[patch 4/4] improve idle cputime accounting

[Martin Schwidefsky <schwidefsky@de.ibm.com>]

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From: Martin Schwidefsky <schwidefsky@de.ibm.com>

Distinguish the cputime of the idle process where idle is actually using
cpu cycles from the cputime where idle is sleeping on an enabled wait psw.
The former is acconuted as system time, the later as idle time.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

 arch/s390/include/asm/cpu.h |    1 +
 arch/s390/kernel/process.c  |    7 +++++++
 arch/s390/kernel/s390_ext.c |    2 +-
 arch/s390/kernel/vtime.c    |   24 ++++++------------------
 drivers/s390/cio/cio.c      |    2 +-
 5 files changed, 16 insertions(+), 20 deletions(-)

Index: linux-idle/arch/s390/include/asm/cpu.h
===================================================================
--- linux-idle.orig/arch/s390/include/asm/cpu.h
+++ linux-idle/arch/s390/include/asm/cpu.h
@@ -15,6 +15,7 @@
 struct s390_idle_data {
 	spinlock_t lock;
 	unsigned long long idle_count;
+	unsigned long long idle_delta;
 	unsigned long long idle_enter;
 	unsigned long long idle_time;
 };
Index: linux-idle/arch/s390/kernel/process.c
===================================================================
--- linux-idle.orig/arch/s390/kernel/process.c
+++ linux-idle/arch/s390/kernel/process.c
@@ -87,6 +87,13 @@ void s390_idle_leave(void)
 
 	idle = &__get_cpu_var(s390_idle);
 	idle_time = S390_lowcore.int_clock - idle->idle_enter;
+#ifdef CONFIG_VIRT_CPU_ACCOUNTING
+	idle_time += idle->idle_delta;
+	idle->idle_delta = idle_time & 4095;
+	idle_time -= idle->idle_delta;
+	account_idle_time(idle_time >> 12);
+	S390_lowcore.last_update_clock = S390_lowcore.int_clock;
+#endif
 	spin_lock(&idle->lock);
 	idle->idle_time += idle_time;
 	idle->idle_enter = 0ULL;
Index: linux-idle/arch/s390/kernel/s390_ext.c
===================================================================
--- linux-idle.orig/arch/s390/kernel/s390_ext.c
+++ linux-idle/arch/s390/kernel/s390_ext.c
@@ -119,8 +119,8 @@ void do_extint(struct pt_regs *regs, uns
 	struct pt_regs *old_regs;
 
 	old_regs = set_irq_regs(regs);
-	irq_enter();
 	s390_idle_check();
+	irq_enter();
 	if (S390_lowcore.int_clock >= S390_lowcore.clock_comparator)
 		/* Serve timer interrupts first. */
 		clock_comparator_work();
Index: linux-idle/arch/s390/kernel/vtime.c
===================================================================
--- linux-idle.orig/arch/s390/kernel/vtime.c
+++ linux-idle/arch/s390/kernel/vtime.c
@@ -56,19 +56,13 @@ void account_process_tick(struct task_st
 	cputime =  S390_lowcore.system_timer >> 12;
 	S390_lowcore.system_timer -= cputime << 12;
 	S390_lowcore.steal_clock -= cputime << 12;
-	if (idle_task(smp_processor_id()) != current)
-		account_system_time(tsk, HARDIRQ_OFFSET, cputime, cputime);
-	else
-		account_idle_time(cputime);
+	account_system_time(tsk, HARDIRQ_OFFSET, cputime, cputime);
 
 	cputime = S390_lowcore.steal_clock;
 	if ((__s64) cputime > 0) {
 		cputime >>= 12;
 		S390_lowcore.steal_clock -= cputime << 12;
-		if (idle_task(smp_processor_id()) != current)
-			account_steal_time(cputime);
-		else
-			account_idle_time(cputime);
+		account_steal_time(cputime);
 	}
 }
 
@@ -94,10 +88,7 @@ void account_vtime(struct task_struct *t
 	cputime =  S390_lowcore.system_timer >> 12;
 	S390_lowcore.system_timer -= cputime << 12;
 	S390_lowcore.steal_clock -= cputime << 12;
-	if (idle_task(smp_processor_id()) != current)
-		account_system_time(tsk, 0, cputime, cputime);
-	else
-		account_idle_time(cputime);
+	account_system_time(tsk, 0, cputime, cputime);
 }
 
 /*
@@ -117,10 +108,7 @@ void account_system_vtime(struct task_st
 	cputime =  S390_lowcore.system_timer >> 12;
 	S390_lowcore.system_timer -= cputime << 12;
 	S390_lowcore.steal_clock -= cputime << 12;
-	if (in_irq() || idle_task(smp_processor_id()) != current)
-		account_system_time(tsk, 0, cputime, cputime);
-	else
-		account_idle_time(cputime);
+	account_system_time(tsk, 0, cputime, cputime);
 }
 EXPORT_SYMBOL_GPL(account_system_vtime);
 
@@ -158,8 +146,8 @@ void vtime_start_cpu_timer(void)
 	if (vt_list->idle & 1LL<<63)
 		return;
 
-	if (!list_empty(&vt_list->list))
-		set_vtimer(vt_list->idle);
+	S390_lowcore.last_update_timer = S390_lowcore.async_enter_timer;
+	set_vtimer(vt_list->idle);
 }
 
 void vtime_stop_cpu_timer(void)
Index: linux-idle/drivers/s390/cio/cio.c
===================================================================
--- linux-idle.orig/drivers/s390/cio/cio.c
+++ linux-idle/drivers/s390/cio/cio.c
@@ -626,8 +626,8 @@ do_IRQ (struct pt_regs *regs)
 	struct pt_regs *old_regs;
 
 	old_regs = set_irq_regs(regs);
-	irq_enter();
 	s390_idle_check();
+	irq_enter();
 	if (S390_lowcore.int_clock >= S390_lowcore.clock_comparator)
 		/* Serve timer interrupts first. */
 		clock_comparator_work();

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.