From abf917cd91cbb73952758f9741e2fa65002a48ee Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 25 Jul 2012 07:56:04 +0200 Subject: cputime: Generic on-demand virtual cputime accounting If we want to stop the tick further idle, we need to be able to account the cputime without using the tick. Virtual based cputime accounting solves that problem by hooking into kernel/user boundaries. However implementing CONFIG_VIRT_CPU_ACCOUNTING require low level hooks and involves more overhead. But we already have a generic context tracking subsystem that is required for RCU needs by archs which plan to shut down the tick outside idle. This patch implements a generic virtual based cputime accounting that relies on these generic kernel/user hooks. There are some upsides of doing this: - This requires no arch code to implement CONFIG_VIRT_CPU_ACCOUNTING if context tracking is already built (already necessary for RCU in full tickless mode). - We can rely on the generic context tracking subsystem to dynamically (de)activate the hooks, so that we can switch anytime between virtual and tick based accounting. This way we don't have the overhead of the virtual accounting when the tick is running periodically. And one downside: - There is probably more overhead than a native virtual based cputime accounting. But this relies on hooks that are already set anyway. Signed-off-by: Frederic Weisbecker Cc: Andrew Morton Cc: Ingo Molnar Cc: Li Zhong Cc: Namhyung Kim Cc: Paul E. McKenney Cc: Paul Gortmaker Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner --- arch/ia64/kernel/time.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/ia64/kernel/time.c') diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c index 88a794536bc0..a3a3f5a1cb3a 100644 --- a/arch/ia64/kernel/time.c +++ b/arch/ia64/kernel/time.c @@ -77,7 +77,7 @@ static struct clocksource clocksource_itc = { }; static struct clocksource *itc_clocksource; -#ifdef CONFIG_VIRT_CPU_ACCOUNTING +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE #include @@ -142,7 +142,7 @@ void vtime_account_idle(struct task_struct *tsk) account_idle_time(vtime_delta(tsk)); } -#endif /* CONFIG_VIRT_CPU_ACCOUNTING */ +#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */ static irqreturn_t timer_interrupt (int irq, void *dev_id) -- cgit v1.2.3-70-g09d2 From c11f11fcbdb5be790c565aed46411486a7586afc Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 21 Jan 2013 00:50:22 +0100 Subject: kvm: Prepare to add generic guest entry/exit callbacks Do some ground preparatory work before adding guest_enter() and guest_exit() context tracking callbacks. Those will be later used to read the guest cputime safely when we run in full dynticks mode. Signed-off-by: Frederic Weisbecker Cc: Andrew Morton Cc: Gleb Natapov Cc: Ingo Molnar Cc: Li Zhong Cc: Marcelo Tosatti Cc: Namhyung Kim Cc: Paul E. McKenney Cc: Paul Gortmaker Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner --- arch/ia64/kernel/time.c | 1 + arch/powerpc/kernel/time.c | 1 + include/linux/kvm_host.h | 39 ++++++++++++++++++++++++++++++--------- include/linux/vtime.h | 2 -- kernel/sched/cputime.c | 10 ---------- 5 files changed, 32 insertions(+), 21 deletions(-) (limited to 'arch/ia64/kernel/time.c') diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c index a3a3f5a1cb3a..fbaac1afb844 100644 --- a/arch/ia64/kernel/time.c +++ b/arch/ia64/kernel/time.c @@ -136,6 +136,7 @@ void vtime_account_system(struct task_struct *tsk) account_system_time(tsk, 0, delta, delta); } +EXPORT_SYMBOL_GPL(vtime_account_system); void vtime_account_idle(struct task_struct *tsk) { diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 22c9b67f9983..2e04b37f67f9 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -347,6 +347,7 @@ void vtime_account_system(struct task_struct *tsk) if (stolen) account_steal_time(stolen); } +EXPORT_SYMBOL_GPL(vtime_account_system); void vtime_account_idle(struct task_struct *tsk) { diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 2c497ab0d03d..4fe2396401da 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -22,6 +22,7 @@ #include #include #include +#include #include #include @@ -740,15 +741,36 @@ static inline int kvm_deassign_device(struct kvm *kvm, } #endif /* CONFIG_IOMMU_API */ -static inline void kvm_guest_enter(void) +static inline void guest_enter(void) { - BUG_ON(preemptible()); /* * This is running in ioctl context so we can avoid * the call to vtime_account() with its unnecessary idle check. */ - vtime_account_system_irqsafe(current); + vtime_account_system(current); current->flags |= PF_VCPU; +} + +static inline void guest_exit(void) +{ + /* + * This is running in ioctl context so we can avoid + * the call to vtime_account() with its unnecessary idle check. + */ + vtime_account_system(current); + current->flags &= ~PF_VCPU; +} + +static inline void kvm_guest_enter(void) +{ + unsigned long flags; + + BUG_ON(preemptible()); + + local_irq_save(flags); + guest_enter(); + local_irq_restore(flags); + /* KVM does not hold any references to rcu protected data when it * switches CPU into a guest mode. In fact switching to a guest mode * is very similar to exiting to userspase from rcu point of view. In @@ -761,12 +783,11 @@ static inline void kvm_guest_enter(void) static inline void kvm_guest_exit(void) { - /* - * This is running in ioctl context so we can avoid - * the call to vtime_account() with its unnecessary idle check. - */ - vtime_account_system_irqsafe(current); - current->flags &= ~PF_VCPU; + unsigned long flags; + + local_irq_save(flags); + guest_exit(); + local_irq_restore(flags); } /* diff --git a/include/linux/vtime.h b/include/linux/vtime.h index 5368af9bdf06..bb50c3ca0d79 100644 --- a/include/linux/vtime.h +++ b/include/linux/vtime.h @@ -6,7 +6,6 @@ struct task_struct; #ifdef CONFIG_VIRT_CPU_ACCOUNTING extern void vtime_task_switch(struct task_struct *prev); extern void vtime_account_system(struct task_struct *tsk); -extern void vtime_account_system_irqsafe(struct task_struct *tsk); extern void vtime_account_idle(struct task_struct *tsk); extern void vtime_account_user(struct task_struct *tsk); extern void vtime_account(struct task_struct *tsk); @@ -20,7 +19,6 @@ static inline bool vtime_accounting_enabled(void) { return true; } #else /* !CONFIG_VIRT_CPU_ACCOUNTING */ static inline void vtime_task_switch(struct task_struct *prev) { } static inline void vtime_account_system(struct task_struct *tsk) { } -static inline void vtime_account_system_irqsafe(struct task_struct *tsk) { } static inline void vtime_account_user(struct task_struct *tsk) { } static inline void vtime_account(struct task_struct *tsk) { } static inline bool vtime_accounting_enabled(void) { return false; } diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index c533deaf06d5..a44ecdf809a1 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -465,16 +465,6 @@ void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime *st = cputime.stime; } -void vtime_account_system_irqsafe(struct task_struct *tsk) -{ - unsigned long flags; - - local_irq_save(flags); - vtime_account_system(tsk); - local_irq_restore(flags); -} -EXPORT_SYMBOL_GPL(vtime_account_system_irqsafe); - #ifndef __ARCH_HAS_VTIME_TASK_SWITCH void vtime_task_switch(struct task_struct *prev) { -- cgit v1.2.3-70-g09d2