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Subject[PATCH 03/12] lib: dampen the percpu_counter FBC_BATCH
With the current logic the percpu_counter's accuracy delta is quadric
wrt the number of cpus in the system, reduce this to O(n ln n).

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/linux/percpu_counter.h | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

Index: linux-2.6-mm/include/linux/percpu_counter.h
===================================================================
--- linux-2.6-mm.orig/include/linux/percpu_counter.h
+++ linux-2.6-mm/include/linux/percpu_counter.h
@@ -11,6 +11,7 @@
#include <linux/threads.h>
#include <linux/percpu.h>
#include <linux/types.h>
+#include <linux/log2.h>

#ifdef CONFIG_SMP

@@ -20,11 +21,7 @@ struct percpu_counter {
s32 *counters;
};

-#if NR_CPUS >= 16
-#define FBC_BATCH (NR_CPUS*2)
-#else
-#define FBC_BATCH (NR_CPUS*4)
-#endif
+#define FBC_BATCH (8*ilog2(NR_CPUS))

static inline void percpu_counter_init(struct percpu_counter *fbc, s64 amount)
{
--

-
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