Re: [thiscpuops upgrade 10/10] Lockless (and preemptless) fastpathsfor slub

[Christoph Lameter]

Use power of two increment in all cases.

Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2010-11-23 22:22:03.596998064 -0600
+++ linux-2.6/mm/slub.c	2010-11-23 21:53:09.422591631 -0600
@@ -1490,19 +1490,21 @@
  * during cmpxchg. The transactions start with the cpu number and are then
  * incremented by CONFIG_NR_CPUS.
  */
+#define TID_STEP  roundup_pow_of_two(CONFIG_NR_CPUS)
+
 static inline unsigned long next_tid(unsigned long tid)
 {
-	return tid + CONFIG_NR_CPUS;
+	return tid + TID_STEP;
 }

 static inline unsigned int tid_to_cpu(unsigned long tid)
 {
-	return tid % CONFIG_NR_CPUS;
+	return tid % TID_STEP;
 }

 static inline unsigned long tid_to_event(unsigned long tid)
 {
-	return tid / CONFIG_NR_CPUS;
+	return tid / TID_STEP;
 }

 static inline unsigned int init_tid(int cpu)

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