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/spinlock.h>
10 #include <linux/smp.h>
11 #include <linux/threads.h>
12 #include <linux/percpu.h>
16 struct percpu_counter {
23 #define FBC_BATCH (NR_CPUS*2)
25 #define FBC_BATCH (NR_CPUS*4)
28 static inline void percpu_counter_init(struct percpu_counter *fbc)
30 spin_lock_init(&fbc->lock);
32 fbc->counters = alloc_percpu(long);
35 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
37 free_percpu(fbc->counters);
40 void percpu_counter_mod(struct percpu_counter *fbc, long amount);
41 long percpu_counter_sum(struct percpu_counter *fbc);
43 static inline long percpu_counter_read(struct percpu_counter *fbc)
49 * It is possible for the percpu_counter_read() to return a small negative
50 * number for some counter which should never be negative.
52 static inline long percpu_counter_read_positive(struct percpu_counter *fbc)
54 long ret = fbc->count;
56 barrier(); /* Prevent reloads of fbc->count */
64 struct percpu_counter {
68 static inline void percpu_counter_init(struct percpu_counter *fbc)
73 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
78 percpu_counter_mod(struct percpu_counter *fbc, long amount)
85 static inline long percpu_counter_read(struct percpu_counter *fbc)
90 static inline long percpu_counter_read_positive(struct percpu_counter *fbc)
95 static inline long percpu_counter_sum(struct percpu_counter *fbc)
97 return percpu_counter_read_positive(fbc);
100 #endif /* CONFIG_SMP */
102 static inline void percpu_counter_inc(struct percpu_counter *fbc)
104 percpu_counter_mod(fbc, 1);
107 static inline void percpu_counter_dec(struct percpu_counter *fbc)
109 percpu_counter_mod(fbc, -1);
112 #endif /* _LINUX_PERCPU_COUNTER_H */