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include/linux/proportions.h 3.09 KB
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145ca25eb   Peter Zijlstra   lib: floating pro... 
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  /*
   * FLoating proportions
   *
   *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
   *
   * This file contains the public data structure and API definitions.
   */
  
  #ifndef _LINUX_PROPORTIONS_H
  #define _LINUX_PROPORTIONS_H
  
  #include <linux/percpu_counter.h>
  #include <linux/spinlock.h>
  #include <linux/mutex.h>
  
  struct prop_global {
  	/*
  	 * The period over which we differentiate
  	 *
  	 *   period = 2^shift
  	 */
  	int shift;
  	/*
  	 * The total event counter aka 'time'.
  	 *
  	 * Treated as an unsigned long; the lower 'shift - 1' bits are the
  	 * counter bits, the remaining upper bits the period counter.
  	 */
  	struct percpu_counter events;
  };
  
  /*
   * global proportion descriptor
   *
   * this is needed to consitently flip prop_global structures.
   */
  struct prop_descriptor {
  	int index;
  	struct prop_global pg[2];
  	struct mutex mutex;		/* serialize the prop_global switch */
  };
  
  int prop_descriptor_init(struct prop_descriptor *pd, int shift);
  void prop_change_shift(struct prop_descriptor *pd, int new_shift);
  
  /*
   * ----- PERCPU ------
   */
  
  struct prop_local_percpu {
  	/*
  	 * the local events counter
  	 */
  	struct percpu_counter events;
  
  	/*
  	 * snapshot of the last seen global state
  	 */
  	int shift;
  	unsigned long period;
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  	raw_spinlock_t lock;		/* protect the snapshot state */
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  };
  
  int prop_local_init_percpu(struct prop_local_percpu *pl);
  void prop_local_destroy_percpu(struct prop_local_percpu *pl);
  void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl);
  void prop_fraction_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl,
  		long *numerator, long *denominator);
  
  static inline
  void prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
  {
  	unsigned long flags;
  
  	local_irq_save(flags);
  	__prop_inc_percpu(pd, pl);
  	local_irq_restore(flags);
  }
  
  /*
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   * Limit the time part in order to ensure there are some bits left for the
   * cycle counter and fraction multiply.
   */
  #define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
  
  #define PROP_FRAC_SHIFT		(BITS_PER_LONG - PROP_MAX_SHIFT - 1)
  #define PROP_FRAC_BASE		(1UL << PROP_FRAC_SHIFT)
  
  void __prop_inc_percpu_max(struct prop_descriptor *pd,
  			   struct prop_local_percpu *pl, long frac);
  
  
  /*
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   * ----- SINGLE ------
   */
  
  struct prop_local_single {
  	/*
  	 * the local events counter
  	 */
  	unsigned long events;
  
  	/*
  	 * snapshot of the last seen global state
  	 * and a lock protecting this state
  	 */
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  	unsigned long period;
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  	int shift;
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  	raw_spinlock_t lock;		/* protect the snapshot state */
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  };
  
  #define INIT_PROP_LOCAL_SINGLE(name)			\
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  {	.lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock),	\
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  }
  
  int prop_local_init_single(struct prop_local_single *pl);
  void prop_local_destroy_single(struct prop_local_single *pl);
  void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl);
  void prop_fraction_single(struct prop_descriptor *pd, struct prop_local_single *pl,
  		long *numerator, long *denominator);
  
  static inline
  void prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
  {
  	unsigned long flags;
  
  	local_irq_save(flags);
  	__prop_inc_single(pd, pl);
  	local_irq_restore(flags);
  }
  
  #endif /* _LINUX_PROPORTIONS_H */