850449080e1cfb7f619eca4ae5d5ed6aca01a1d0
[linux-2.6.git] / lib / percpu_counter.c
1 /*
2  * Fast batching percpu counters.
3  */
4
5 #include <linux/percpu_counter.h>
6 #include <linux/module.h>
7
8 void percpu_counter_mod(struct percpu_counter *fbc, s32 amount)
9 {
10         long count;
11         s32 *pcount;
12         int cpu = get_cpu();
13
14         pcount = per_cpu_ptr(fbc->counters, cpu);
15         count = *pcount + amount;
16         if (count >= FBC_BATCH || count <= -FBC_BATCH) {
17                 spin_lock(&fbc->lock);
18                 fbc->count += count;
19                 *pcount = 0;
20                 spin_unlock(&fbc->lock);
21         } else {
22                 *pcount = count;
23         }
24         put_cpu();
25 }
26 EXPORT_SYMBOL(percpu_counter_mod);
27
28 /*
29  * Add up all the per-cpu counts, return the result.  This is a more accurate
30  * but much slower version of percpu_counter_read_positive()
31  */
32 s64 percpu_counter_sum(struct percpu_counter *fbc)
33 {
34         s64 ret;
35         int cpu;
36
37         spin_lock(&fbc->lock);
38         ret = fbc->count;
39         for_each_possible_cpu(cpu) {
40                 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
41                 ret += *pcount;
42         }
43         spin_unlock(&fbc->lock);
44         return ret < 0 ? 0 : ret;
45 }
46 EXPORT_SYMBOL(percpu_counter_sum);