1 #ifndef _LINUX_PERCPU_COUNTER_H
2 #define _LINUX_PERCPU_COUNTER_H
4 * A simple "approximate counter" for use in ext2 and ext3 superblocks.
6 * WARNING: these things are HUGE. 4 kbytes per counter on 32-way P4.
9 #include <linux/config.h>
10 #include <linux/spinlock.h>
11 #include <linux/smp.h>
12 #include <linux/threads.h>
13 #include <linux/percpu.h>
17 struct percpu_counter {
24 #define FBC_BATCH (NR_CPUS*2)
26 #define FBC_BATCH (NR_CPUS*4)
29 static inline void percpu_counter_init(struct percpu_counter *fbc)
31 spin_lock_init(&fbc->lock);
33 fbc->counters = alloc_percpu(long);
36 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
38 free_percpu(fbc->counters);
41 void percpu_counter_mod(struct percpu_counter *fbc, long amount);
42 long percpu_counter_sum(struct percpu_counter *fbc);
44 static inline long percpu_counter_read(struct percpu_counter *fbc)
50 * It is possible for the percpu_counter_read() to return a small negative
51 * number for some counter which should never be negative.
53 static inline long percpu_counter_read_positive(struct percpu_counter *fbc)
55 long ret = fbc->count;
57 barrier(); /* Prevent reloads of fbc->count */
65 struct percpu_counter {
69 static inline void percpu_counter_init(struct percpu_counter *fbc)
74 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
79 percpu_counter_mod(struct percpu_counter *fbc, long amount)
86 static inline long percpu_counter_read(struct percpu_counter *fbc)
91 static inline long percpu_counter_read_positive(struct percpu_counter *fbc)
96 static inline long percpu_counter_sum(struct percpu_counter *fbc)
98 return percpu_counter_read_positive(fbc);
101 #endif /* CONFIG_SMP */
103 static inline void percpu_counter_inc(struct percpu_counter *fbc)
105 percpu_counter_mod(fbc, 1);
108 static inline void percpu_counter_dec(struct percpu_counter *fbc)
110 percpu_counter_mod(fbc, -1);
113 #endif /* _LINUX_PERCPU_COUNTER_H */