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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /include/linux/percpu_counter.h
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'include/linux/percpu_counter.h')
-rw-r--r--include/linux/percpu_counter.h107
1 files changed, 107 insertions, 0 deletions
diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h
new file mode 100644
index 00000000000..bd6708e2c02
--- /dev/null
+++ b/include/linux/percpu_counter.h
@@ -0,0 +1,107 @@
+#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);
+
+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;
+}
+
+#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 */