abf917cd91
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 <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
65 lines
2.2 KiB
C
65 lines
2.2 KiB
C
#ifndef _LINUX_KERNEL_VTIME_H
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#define _LINUX_KERNEL_VTIME_H
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struct task_struct;
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING
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extern void vtime_task_switch(struct task_struct *prev);
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extern void vtime_account_system(struct task_struct *tsk);
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extern void vtime_account_system_irqsafe(struct task_struct *tsk);
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extern void vtime_account_idle(struct task_struct *tsk);
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extern void vtime_account_user(struct task_struct *tsk);
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extern void vtime_account(struct task_struct *tsk);
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#else
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static inline void vtime_task_switch(struct task_struct *prev) { }
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static inline void vtime_account_system(struct task_struct *tsk) { }
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static inline void vtime_account_system_irqsafe(struct task_struct *tsk) { }
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static inline void vtime_account_user(struct task_struct *tsk) { }
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static inline void vtime_account(struct task_struct *tsk) { }
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#endif
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
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static inline void arch_vtime_task_switch(struct task_struct *tsk) { }
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static inline void vtime_user_enter(struct task_struct *tsk)
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{
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vtime_account_system(tsk);
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}
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static inline void vtime_user_exit(struct task_struct *tsk)
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{
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vtime_account_user(tsk);
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}
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#else
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static inline void vtime_user_enter(struct task_struct *tsk) { }
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static inline void vtime_user_exit(struct task_struct *tsk) { }
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#endif
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#ifdef CONFIG_IRQ_TIME_ACCOUNTING
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extern void irqtime_account_irq(struct task_struct *tsk);
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#else
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static inline void irqtime_account_irq(struct task_struct *tsk) { }
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#endif
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static inline void vtime_account_irq_enter(struct task_struct *tsk)
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{
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/*
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* Hardirq can interrupt idle task anytime. So we need vtime_account()
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* that performs the idle check in CONFIG_VIRT_CPU_ACCOUNTING.
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* Softirq can also interrupt idle task directly if it calls
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* local_bh_enable(). Such case probably don't exist but we never know.
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* Ksoftirqd is not concerned because idle time is flushed on context
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* switch. Softirqs in the end of hardirqs are also not a problem because
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* the idle time is flushed on hardirq time already.
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*/
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vtime_account(tsk);
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irqtime_account_irq(tsk);
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}
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static inline void vtime_account_irq_exit(struct task_struct *tsk)
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{
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/* On hard|softirq exit we always account to hard|softirq cputime */
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vtime_account_system(tsk);
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irqtime_account_irq(tsk);
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}
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#endif /* _LINUX_KERNEL_VTIME_H */
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