From: Eric Dumazet <dada1@cosmosbay.com>

percpu_data blindly allocates bootmem memory to store NR_CPUS instances of
cpudata, instead of allocating memory only for possible cpus.

This patch saves ram, allocating num_possible_cpus() (instead of NR_CPUS)
instances.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: Jens Axboe <axboe@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Jens Axboe <axboe@suse.de>
Cc: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 init/main.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff -puN init/main.c~only-allocate-percpu-data-for-possible-cpus init/main.c
--- devel/init/main.c~only-allocate-percpu-data-for-possible-cpus	2006-02-03 01:00:25.000000000 -0800
+++ devel-akpm/init/main.c	2006-02-03 01:00:25.000000000 -0800
@@ -333,6 +333,7 @@ static void __init setup_per_cpu_areas(v
 {
 	unsigned long size, i;
 	char *ptr;
+	unsigned long nr_possible_cpus = num_possible_cpus();
 
 	/* Copy section for each CPU (we discard the original) */
 	size = ALIGN(__per_cpu_end - __per_cpu_start, SMP_CACHE_BYTES);
@@ -340,12 +341,16 @@ static void __init setup_per_cpu_areas(v
 	if (size < PERCPU_ENOUGH_ROOM)
 		size = PERCPU_ENOUGH_ROOM;
 #endif
+	ptr = alloc_bootmem(size * nr_possible_cpus);
 
-	ptr = alloc_bootmem(size * NR_CPUS);
-
-	for (i = 0; i < NR_CPUS; i++, ptr += size) {
+	for (i = 0; i < NR_CPUS; i++) {
+		if (!cpu_possible(i)) {
+			__per_cpu_offset[i] = (char*)0 - __per_cpu_start;
+			continue;
+		}
 		__per_cpu_offset[i] = ptr - __per_cpu_start;
 		memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start);
+		ptr += size;
 	}
 }
 #endif /* !__GENERIC_PER_CPU */
_