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8d495477d6
On context switch we are locking the vtime seqcount of the scheduling-out task twice: * On vtime_task_switch_common(), when we flush the pending vtime through vtime_account_system() * On arch_vtime_task_switch() to reset the vtime state. This is pointless as these actions can be performed without the need to unlock/lock in the middle. The reason these steps are separated is to consolidate a very small amount of common code between CONFIG_VIRT_CPU_ACCOUNTING_GEN and CONFIG_VIRT_CPU_ACCOUNTING_NATIVE. Performance in this fast path is definitely a priority over artificial code factorization so split the task switch code between GEN and NATIVE and mutualize the parts than can run under a single seqcount locked block. As a side effect, vtime_account_idle() becomes included in the seqcount protection. This happens to be a welcome preparation in order to properly support kcpustat under vtime in the future and fetch CPUTIME_IDLE without race. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Wanpeng Li <wanpengli@tencent.com> Cc: Yauheni Kaliuta <yauheni.kaliuta@redhat.com> Link: https://lkml.kernel.org/r/20191003161745.28464-3-frederic@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
118 lines
3.5 KiB
C
118 lines
3.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_KERNEL_VTIME_H
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#define _LINUX_KERNEL_VTIME_H
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#include <linux/context_tracking_state.h>
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
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#include <asm/vtime.h>
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#endif
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struct task_struct;
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/*
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* vtime_accounting_cpu_enabled() definitions/declarations
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*/
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#if defined(CONFIG_VIRT_CPU_ACCOUNTING_NATIVE)
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static inline bool vtime_accounting_cpu_enabled(void) { return true; }
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extern void vtime_task_switch(struct task_struct *prev);
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#elif defined(CONFIG_VIRT_CPU_ACCOUNTING_GEN)
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/*
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* Checks if vtime is enabled on some CPU. Cputime readers want to be careful
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* in that case and compute the tickless cputime.
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* For now vtime state is tied to context tracking. We might want to decouple
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* those later if necessary.
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*/
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static inline bool vtime_accounting_enabled(void)
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{
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return context_tracking_is_enabled();
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}
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static inline bool vtime_accounting_cpu_enabled(void)
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{
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if (vtime_accounting_enabled()) {
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if (context_tracking_cpu_is_enabled())
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return true;
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}
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return false;
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}
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extern void vtime_task_switch_generic(struct task_struct *prev);
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static inline void vtime_task_switch(struct task_struct *prev)
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{
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if (vtime_accounting_cpu_enabled())
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vtime_task_switch_generic(prev);
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}
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#else /* !CONFIG_VIRT_CPU_ACCOUNTING */
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static inline bool vtime_accounting_cpu_enabled(void) { return false; }
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static inline void vtime_task_switch(struct task_struct *prev) { }
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#endif
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/*
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* Common vtime APIs
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*/
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING
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extern void vtime_account_kernel(struct task_struct *tsk);
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extern void vtime_account_idle(struct task_struct *tsk);
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#else /* !CONFIG_VIRT_CPU_ACCOUNTING */
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static inline void vtime_account_kernel(struct task_struct *tsk) { }
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#endif /* !CONFIG_VIRT_CPU_ACCOUNTING */
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
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extern void arch_vtime_task_switch(struct task_struct *tsk);
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extern void vtime_user_enter(struct task_struct *tsk);
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extern void vtime_user_exit(struct task_struct *tsk);
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extern void vtime_guest_enter(struct task_struct *tsk);
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extern void vtime_guest_exit(struct task_struct *tsk);
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extern void vtime_init_idle(struct task_struct *tsk, int cpu);
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#else /* !CONFIG_VIRT_CPU_ACCOUNTING_GEN */
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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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static inline void vtime_guest_enter(struct task_struct *tsk) { }
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static inline void vtime_guest_exit(struct task_struct *tsk) { }
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static inline void vtime_init_idle(struct task_struct *tsk, int cpu) { }
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#endif
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
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extern void vtime_account_irq_enter(struct task_struct *tsk);
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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_kernel(tsk);
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}
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extern void vtime_flush(struct task_struct *tsk);
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#else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
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static inline void vtime_account_irq_enter(struct task_struct *tsk) { }
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static inline void vtime_account_irq_exit(struct task_struct *tsk) { }
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static inline void vtime_flush(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 account_irq_enter_time(struct task_struct *tsk)
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{
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vtime_account_irq_enter(tsk);
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irqtime_account_irq(tsk);
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}
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static inline void account_irq_exit_time(struct task_struct *tsk)
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{
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vtime_account_irq_exit(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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