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authorAndrew Morton <akpm@linux-foundation.org>2007-07-15 23:39:51 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 09:05:41 -0700
commitc67ad917cbf21b2862e2cf8e8b28339872ef7927 (patch)
tree362d8cf8668998b8cd5deb611693f584b8df5ee5 /include
parent85420ccad1610f123365eec89848ef25641bc6b7 (diff)
percpu_counters(): use cpu notifiers
per-cpu counters presently must iterate over all possible CPUs in the exhaustive percpu_counter_sum(). But it can be much better to only iterate over the presently-online CPUs. To do this, we must arrange for an offlined CPU's count to be spilled into the counter's central count. We can do this for all percpu_counters in the machine by linking them into a single global list and walking that list at CPU_DEAD time. (I hope. Might have race windows in which the percpu_counter_sum() count is inaccurate?) Cc: Gautham R Shenoy <ego@in.ibm.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/percpu_counter.h18
1 files changed, 6 insertions, 12 deletions
diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h
index f5aa593ccf3..3d9f70972cd 100644
--- a/include/linux/percpu_counter.h
+++ b/include/linux/percpu_counter.h
@@ -8,6 +8,7 @@
#include <linux/spinlock.h>
#include <linux/smp.h>
+#include <linux/list.h>
#include <linux/threads.h>
#include <linux/percpu.h>
#include <linux/types.h>
@@ -17,6 +18,9 @@
struct percpu_counter {
spinlock_t lock;
s64 count;
+#ifdef CONFIG_HOTPLUG_CPU
+ struct list_head list; /* All percpu_counters are on a list */
+#endif
s32 *counters;
};
@@ -26,18 +30,8 @@ struct percpu_counter {
#define FBC_BATCH (NR_CPUS*4)
#endif
-static inline void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
-{
- spin_lock_init(&fbc->lock);
- fbc->count = amount;
- fbc->counters = alloc_percpu(s32);
-}
-
-static inline void percpu_counter_destroy(struct percpu_counter *fbc)
-{
- free_percpu(fbc->counters);
-}
-
+void percpu_counter_init(struct percpu_counter *fbc, s64 amount);
+void percpu_counter_destroy(struct percpu_counter *fbc);
void percpu_counter_mod(struct percpu_counter *fbc, s32 amount);
s64 percpu_counter_sum(struct percpu_counter *fbc);