From 79741dd35713ff4f6fd0eafd59fa94e8a4ba922d Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Wed, 31 Dec 2008 15:11:38 +0100 Subject: [PATCH] idle cputime accounting The cpu time spent by the idle process actually doing something is currently accounted as idle time. This is plain wrong, the architectures that support VIRT_CPU_ACCOUNTING=y can do better: distinguish between the time spent doing nothing and the time spent by idle doing work. The first is accounted with account_idle_time and the second with account_system_time. The architectures that use the account_xxx_time interface directly and not the account_xxx_ticks interface now need to do the check for the idle process in their arch code. In particular to improve the system vs true idle time accounting the arch code needs to measure the true idle time instead of just testing for the idle process. To improve the tick based accounting as well we would need an architecture primitive that can tell us if the pt_regs of the interrupted context points to the magic instruction that halts the cpu. In addition idle time is no more added to the stime of the idle process. This field now contains the system time of the idle process as it should be. On systems without VIRT_CPU_ACCOUNTING this will always be zero as every tick that occurs while idle is running will be accounted as idle time. This patch contains the necessary common code changes to be able to distinguish idle system time and true idle time. The architectures with support for VIRT_CPU_ACCOUNTING need some changes to exploit this. Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/vtime.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) (limited to 'arch/s390') diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c index 07283aea2e5..4a4a34caec5 100644 --- a/arch/s390/kernel/vtime.c +++ b/arch/s390/kernel/vtime.c @@ -55,13 +55,19 @@ void account_process_tick(struct task_struct *tsk, int user_tick) cputime = S390_lowcore.system_timer >> 12; S390_lowcore.system_timer -= cputime << 12; S390_lowcore.steal_clock -= cputime << 12; - account_system_time(tsk, HARDIRQ_OFFSET, cputime, cputime); + if (idle_task(smp_processor_id()) != current) + account_system_time(tsk, HARDIRQ_OFFSET, cputime, cputime); + else + account_idle_time(cputime); cputime = S390_lowcore.steal_clock; if ((__s64) cputime > 0) { cputime >>= 12; S390_lowcore.steal_clock -= cputime << 12; - account_steal_time(tsk, cputime); + if (idle_task(smp_processor_id()) != current) + account_steal_time(cputime); + else + account_idle_time(cputime); } } @@ -87,7 +93,10 @@ void account_vtime(struct task_struct *tsk) cputime = S390_lowcore.system_timer >> 12; S390_lowcore.system_timer -= cputime << 12; S390_lowcore.steal_clock -= cputime << 12; - account_system_time(tsk, 0, cputime, cputime); + if (idle_task(smp_processor_id()) != current) + account_system_time(tsk, 0, cputime, cputime); + else + account_idle_time(cputime); } /* @@ -107,7 +116,10 @@ void account_system_vtime(struct task_struct *tsk) cputime = S390_lowcore.system_timer >> 12; S390_lowcore.system_timer -= cputime << 12; S390_lowcore.steal_clock -= cputime << 12; - account_system_time(tsk, 0, cputime, cputime); + if (in_irq() || idle_task(smp_processor_id()) != current) + account_system_time(tsk, 0, cputime, cputime); + else + account_idle_time(cputime); } EXPORT_SYMBOL_GPL(account_system_vtime); -- cgit v1.2.3