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>
29 lines
964 B
C
29 lines
964 B
C
/*
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* Definitions for measuring cputime on ia64 machines.
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*
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* Based on <asm-powerpc/cputime.h>.
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*
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* Copyright (C) 2007 FUJITSU LIMITED
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* Copyright (C) 2007 Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* If we have CONFIG_VIRT_CPU_ACCOUNTING_NATIVE, we measure cpu time in nsec.
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* Otherwise we measure cpu time in jiffies using the generic definitions.
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*/
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#ifndef __IA64_CPUTIME_H
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#define __IA64_CPUTIME_H
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#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
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# include <asm-generic/cputime.h>
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#else
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# include <asm/processor.h>
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# include <asm-generic/cputime_nsecs.h>
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extern void arch_vtime_task_switch(struct task_struct *tsk);
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#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
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#endif /* __IA64_CPUTIME_H */
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