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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>
104 lines
2.8 KiB
C
104 lines
2.8 KiB
C
/*
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* Definitions for measuring cputime in nsecs resolution.
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*
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* Based on <arch/ia64/include/asm/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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*/
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#ifndef _ASM_GENERIC_CPUTIME_NSECS_H
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#define _ASM_GENERIC_CPUTIME_NSECS_H
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typedef u64 __nocast cputime_t;
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typedef u64 __nocast cputime64_t;
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#define cputime_one_jiffy jiffies_to_cputime(1)
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/*
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* Convert cputime <-> jiffies (HZ)
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*/
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#define cputime_to_jiffies(__ct) \
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((__force u64)(__ct) / (NSEC_PER_SEC / HZ))
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#define cputime_to_scaled(__ct) (__ct)
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#define jiffies_to_cputime(__jif) \
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(__force cputime_t)((__jif) * (NSEC_PER_SEC / HZ))
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#define cputime64_to_jiffies64(__ct) \
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((__force u64)(__ct) / (NSEC_PER_SEC / HZ))
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#define jiffies64_to_cputime64(__jif) \
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(__force cputime64_t)((__jif) * (NSEC_PER_SEC / HZ))
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/*
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* Convert cputime <-> nanoseconds
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*/
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#define nsecs_to_cputime(__nsecs) ((__force u64)(__nsecs))
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/*
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* Convert cputime <-> microseconds
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*/
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#define cputime_to_usecs(__ct) \
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((__force u64)(__ct) / NSEC_PER_USEC)
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#define usecs_to_cputime(__usecs) \
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(__force cputime_t)((__usecs) * NSEC_PER_USEC)
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#define usecs_to_cputime64(__usecs) \
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(__force cputime64_t)((__usecs) * NSEC_PER_USEC)
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/*
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* Convert cputime <-> seconds
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*/
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#define cputime_to_secs(__ct) \
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((__force u64)(__ct) / NSEC_PER_SEC)
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#define secs_to_cputime(__secs) \
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(__force cputime_t)((__secs) * NSEC_PER_SEC)
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/*
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* Convert cputime <-> timespec (nsec)
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*/
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static inline cputime_t timespec_to_cputime(const struct timespec *val)
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{
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u64 ret = val->tv_sec * NSEC_PER_SEC + val->tv_nsec;
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return (__force cputime_t) ret;
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}
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static inline void cputime_to_timespec(const cputime_t ct, struct timespec *val)
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{
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val->tv_sec = (__force u64) ct / NSEC_PER_SEC;
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val->tv_nsec = (__force u64) ct % NSEC_PER_SEC;
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}
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/*
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* Convert cputime <-> timeval (msec)
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*/
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static inline cputime_t timeval_to_cputime(struct timeval *val)
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{
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u64 ret = val->tv_sec * NSEC_PER_SEC + val->tv_usec * NSEC_PER_USEC;
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return (__force cputime_t) ret;
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}
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static inline void cputime_to_timeval(const cputime_t ct, struct timeval *val)
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{
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val->tv_sec = (__force u64) ct / NSEC_PER_SEC;
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val->tv_usec = ((__force u64) ct % NSEC_PER_SEC) / NSEC_PER_USEC;
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}
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/*
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* Convert cputime <-> clock (USER_HZ)
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*/
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#define cputime_to_clock_t(__ct) \
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((__force u64)(__ct) / (NSEC_PER_SEC / USER_HZ))
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#define clock_t_to_cputime(__x) \
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(__force cputime_t)((__x) * (NSEC_PER_SEC / USER_HZ))
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/*
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* Convert cputime64 to clock.
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*/
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#define cputime64_to_clock_t(__ct) \
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cputime_to_clock_t((__force cputime_t)__ct)
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#endif
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