[net-next-2.6.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/threads.h>
#include <linux/percpu.h>
#include <linux/types.h>

#ifdef CONFIG_SMP

struct percpu_counter {
	spinlock_t lock;
	s64 count;
	s32 *counters;
};

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

static inline void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
{
	spin_lock_init(&fbc->lock);
	fbc->count = amount;
	fbc->counters = alloc_percpu(s32);
}

static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{
	free_percpu(fbc->counters);
}

void percpu_counter_mod(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_mod(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_mod(fbc, 1);
}

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

#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>
	10	#include <linux/smp.h>
	11	#include <linux/threads.h>
	12	#include <linux/percpu.h>
0216bfcf	13	#include <linux/types.h>
1da177e4 LT	14
	15	#ifdef CONFIG_SMP
	16
	17	struct percpu_counter {
	18	spinlock_t lock;
0216bfcf MC	19	s64 count;
0216bfcf MC	20	s32 *counters;
1da177e4 LT	21	};
	22
	23	#if NR_CPUS >= 16
	24	#define FBC_BATCH (NR_CPUS*2)
	25	#else
	26	#define FBC_BATCH (NR_CPUS*4)
	27	#endif
	28
0216bfcf	29	static inline void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
1da177e4 LT	30	{
1da177e4 LT	31	spin_lock_init(&fbc->lock);
0216bfcf MC	32	fbc->count = amount;
0216bfcf MC	33	fbc->counters = alloc_percpu(s32);
1da177e4 LT	34	}
	35
	36	static inline void percpu_counter_destroy(struct percpu_counter *fbc)
	37	{
	38	free_percpu(fbc->counters);
	39	}
	40
0216bfcf MC	41	void percpu_counter_mod(struct percpu_counter *fbc, s32 amount);
0216bfcf MC	42	s64 percpu_counter_sum(struct percpu_counter *fbc);
1da177e4	43
0216bfcf	44	static inline s64 percpu_counter_read(struct percpu_counter *fbc)
1da177e4 LT	45	{
	46	return fbc->count;
	47	}
	48
	49	/*
	50	* It is possible for the percpu_counter_read() to return a small negative
	51	* number for some counter which should never be negative.
0216bfcf	52	*
1da177e4	53	*/
0216bfcf	54	static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
1da177e4	55	{
0216bfcf	56	s64 ret = fbc->count;
1da177e4 LT	57
1da177e4 LT	58	barrier(); /* Prevent reloads of fbc->count */
0216bfcf	59	if (ret >= 0)
1da177e4 LT	60	return ret;
	61	return 1;
	62	}
	63
	64	#else
	65
	66	struct percpu_counter {
0216bfcf	67	s64 count;
1da177e4 LT	68	};
1da177e4 LT	69
0216bfcf	70	static inline void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
1da177e4	71	{
0216bfcf	72	fbc->count = amount;
1da177e4 LT	73	}
	74
	75	static inline void percpu_counter_destroy(struct percpu_counter *fbc)
	76	{
	77	}
	78
	79	static inline void
0216bfcf	80	percpu_counter_mod(struct percpu_counter *fbc, s32 amount)
1da177e4 LT	81	{
	82	preempt_disable();
	83	fbc->count += amount;
	84	preempt_enable();
	85	}
	86
0216bfcf	87	static inline s64 percpu_counter_read(struct percpu_counter *fbc)
1da177e4 LT	88	{
	89	return fbc->count;
	90	}
	91
0216bfcf	92	static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
1da177e4 LT	93	{
	94	return fbc->count;
	95	}
	96
0216bfcf	97	static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
e2bab3d9 AM	98	{
	99	return percpu_counter_read_positive(fbc);
	100	}
	101
1da177e4 LT	102	#endif /* CONFIG_SMP */
	103
	104	static inline void percpu_counter_inc(struct percpu_counter *fbc)
	105	{
	106	percpu_counter_mod(fbc, 1);
	107	}
	108
	109	static inline void percpu_counter_dec(struct percpu_counter *fbc)
	110	{
	111	percpu_counter_mod(fbc, -1);
	112	}
	113
	114	#endif /* _LINUX_PERCPU_COUNTER_H */