[deliverable/linux.git] / include / linux / percpu_counter.h

#ifndef _LINUX_PERCPU_COUNTER_H
#define _LINUX_PERCPU_COUNTER_H
/*
 * A simple "approximate counter" for use in ext2 and ext3 superblocks.
 *
 * WARNING: these things are HUGE.  4 kbytes per counter on 32-way P4.
 */

#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/list.h>
#include <linux/threads.h>
#include <linux/percpu.h>
#include <linux/types.h>

#ifdef CONFIG_SMP

struct percpu_counter {
	spinlock_t lock;
	s64 count;
#ifdef CONFIG_HOTPLUG_CPU
	struct list_head list;	/* All percpu_counters are on a list */
#endif
	s32 *counters;
};

#if NR_CPUS >= 16
#define FBC_BATCH	(NR_CPUS*2)
#else
#define FBC_BATCH	(NR_CPUS*4)
#endif

void percpu_counter_init(struct percpu_counter *fbc, s64 amount);
void percpu_counter_destroy(struct percpu_counter *fbc);
void percpu_counter_add(struct percpu_counter *fbc, s32 amount);
s64 percpu_counter_sum(struct percpu_counter *fbc);

static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{
	return fbc->count;
}

/*
 * It is possible for the percpu_counter_read() to return a small negative
 * number for some counter which should never be negative.
 *
 */
static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
{
	s64 ret = fbc->count;

	barrier();		/* Prevent reloads of fbc->count */
	if (ret >= 0)
		return ret;
	return 1;
}

#else

struct percpu_counter {
	s64 count;
};

static inline void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
{
	fbc->count = amount;
}

static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{
}

static inline void
percpu_counter_add(struct percpu_counter *fbc, s32 amount)
{
	preempt_disable();
	fbc->count += amount;
	preempt_enable();
}

static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{
	return fbc->count;
}

static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
{
	return fbc->count;
}

static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
{
	return percpu_counter_read_positive(fbc);
}

#endif	/* CONFIG_SMP */

static inline void percpu_counter_inc(struct percpu_counter *fbc)
{
	percpu_counter_add(fbc, 1);
}

static inline void percpu_counter_dec(struct percpu_counter *fbc)
{
	percpu_counter_add(fbc, -1);
}

static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
{
	percpu_counter_add(fbc, -amount);
}

#endif /* _LINUX_PERCPU_COUNTER_H */
Commit	Line	Data
1da177e4 LT	1	#ifndef _LINUX_PERCPU_COUNTER_H
	2	#define _LINUX_PERCPU_COUNTER_H
	3	/*
	4	* A simple "approximate counter" for use in ext2 and ext3 superblocks.
	5	*
	6	* WARNING: these things are HUGE. 4 kbytes per counter on 32-way P4.
	7	*/
	8
1da177e4 LT	9	#include <linux/spinlock.h>
1da177e4 LT	10	#include <linux/smp.h>
c67ad917	11	#include <linux/list.h>
1da177e4 LT	12	#include <linux/threads.h>
1da177e4 LT	13	#include <linux/percpu.h>
0216bfcf	14	#include <linux/types.h>
1da177e4 LT	15
	16	#ifdef CONFIG_SMP
	17
	18	struct percpu_counter {
	19	spinlock_t lock;
0216bfcf	20	s64 count;
c67ad917 AM	21	#ifdef CONFIG_HOTPLUG_CPU
	22	struct list_head list; /* All percpu_counters are on a list */
	23	#endif
0216bfcf	24	s32 *counters;
1da177e4 LT	25	};
	26
	27	#if NR_CPUS >= 16
	28	#define FBC_BATCH (NR_CPUS*2)
	29	#else
	30	#define FBC_BATCH (NR_CPUS*4)
	31	#endif
	32
c67ad917 AM	33	void percpu_counter_init(struct percpu_counter *fbc, s64 amount);
c67ad917 AM	34	void percpu_counter_destroy(struct percpu_counter *fbc);
aa0dff2d	35	void percpu_counter_add(struct percpu_counter *fbc, s32 amount);
0216bfcf	36	s64 percpu_counter_sum(struct percpu_counter *fbc);
1da177e4	37
0216bfcf	38	static inline s64 percpu_counter_read(struct percpu_counter *fbc)
1da177e4 LT	39	{
	40	return fbc->count;
	41	}
	42
	43	/*
	44	* It is possible for the percpu_counter_read() to return a small negative
	45	* number for some counter which should never be negative.
0216bfcf	46	*
1da177e4	47	*/
0216bfcf	48	static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
1da177e4	49	{
0216bfcf	50	s64 ret = fbc->count;
1da177e4 LT	51
1da177e4 LT	52	barrier(); /* Prevent reloads of fbc->count */
0216bfcf	53	if (ret >= 0)
1da177e4 LT	54	return ret;
	55	return 1;
	56	}
	57
	58	#else
	59
	60	struct percpu_counter {
0216bfcf	61	s64 count;
1da177e4 LT	62	};
1da177e4 LT	63
0216bfcf	64	static inline void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
1da177e4	65	{
0216bfcf	66	fbc->count = amount;
1da177e4 LT	67	}
	68
	69	static inline void percpu_counter_destroy(struct percpu_counter *fbc)
	70	{
	71	}
	72
	73	static inline void
aa0dff2d	74	percpu_counter_add(struct percpu_counter *fbc, s32 amount)
1da177e4 LT	75	{
	76	preempt_disable();
	77	fbc->count += amount;
	78	preempt_enable();
	79	}
	80
0216bfcf	81	static inline s64 percpu_counter_read(struct percpu_counter *fbc)
1da177e4 LT	82	{
	83	return fbc->count;
	84	}
	85
0216bfcf	86	static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
1da177e4 LT	87	{
	88	return fbc->count;
	89	}
	90
0216bfcf	91	static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
e2bab3d9 AM	92	{
	93	return percpu_counter_read_positive(fbc);
	94	}
	95
1da177e4 LT	96	#endif /* CONFIG_SMP */
	97
	98	static inline void percpu_counter_inc(struct percpu_counter *fbc)
	99	{
aa0dff2d	100	percpu_counter_add(fbc, 1);
1da177e4 LT	101	}
	102
	103	static inline void percpu_counter_dec(struct percpu_counter *fbc)
	104	{
aa0dff2d	105	percpu_counter_add(fbc, -1);
1da177e4 LT	106	}
1da177e4 LT	107
3cb4f9fa PZ	108	static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
	109	{
	110	percpu_counter_add(fbc, -amount);
	111	}
	112
1da177e4	113	#endif /* _LINUX_PERCPU_COUNTER_H */