android_kernel_motorola_sm6225/include/linux/percpu_counter.h
Andrew Morton e2bab3d924 [PATCH] percpu_counter_sum()
Implement percpu_counter_sum().  This is a more accurate but slower version of
percpu_counter_read_positive().

We need this for Alex's speedup-ext3_statfs patch and for the nr_file
accounting fix.  Otherwise these things would be too inaccurate on large CPU
counts.

Cc: Ravikiran G Thirumalai <kiran@scalex86.org>
Cc: Alex Tomas <alex@clusterfs.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-08 14:14:01 -08:00

113 lines
2.2 KiB
C

#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/config.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/threads.h>
#include <linux/percpu.h>
#ifdef CONFIG_SMP
struct percpu_counter {
spinlock_t lock;
long count;
long *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)
{
spin_lock_init(&fbc->lock);
fbc->count = 0;
fbc->counters = alloc_percpu(long);
}
static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{
free_percpu(fbc->counters);
}
void percpu_counter_mod(struct percpu_counter *fbc, long amount);
long percpu_counter_sum(struct percpu_counter *fbc);
static inline long 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 long percpu_counter_read_positive(struct percpu_counter *fbc)
{
long ret = fbc->count;
barrier(); /* Prevent reloads of fbc->count */
if (ret > 0)
return ret;
return 1;
}
#else
struct percpu_counter {
long count;
};
static inline void percpu_counter_init(struct percpu_counter *fbc)
{
fbc->count = 0;
}
static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{
}
static inline void
percpu_counter_mod(struct percpu_counter *fbc, long amount)
{
preempt_disable();
fbc->count += amount;
preempt_enable();
}
static inline long percpu_counter_read(struct percpu_counter *fbc)
{
return fbc->count;
}
static inline long percpu_counter_read_positive(struct percpu_counter *fbc)
{
return fbc->count;
}
static inline long 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 */