[PATCH] x86: don't initialise cpu_possible_map to all ones
Initialising cpu_possible_map to all-ones with CONFIG_HOTPLUG_CPU means that
a) All for_each_cpu() loops will iterate across all NR_CPUS CPUs, rather
than over possible ones. That can be quite expensive.
b) Soon we'll be allocating per-cpu areas only for possible CPUs. So with
CPU_MASK_ALL, we'll be wasting memory.
I also switched voyager over to not use CPU_MASK_ALL in the non-CPU-hotplug
case. Should be OK..
I note that parisc is also using CPU_MASK_ALL. Suggest that it stop doing
that.
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Paul Jackson <pj@sgi.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Zwane Mwaikambo <zwane@linuxpower.ca>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 20b446f..60e56c6 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -328,7 +328,7 @@
* bitmap of size NR_CPUS.
*
* #ifdef CONFIG_HOTPLUG_CPU
- * cpu_possible_map - all NR_CPUS bits set
+ * cpu_possible_map - has bit 'cpu' set iff cpu is populatable
* cpu_present_map - has bit 'cpu' set iff cpu is populated
* cpu_online_map - has bit 'cpu' set iff cpu available to scheduler
* #else