[PATCH] Only allocate percpu data for possible CPUs

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>
Acked-by: "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>
Acked-by: William Irwin <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 3 deletions

diff --git a/init/main.c b/init/main.c
index 141e8896d25..9cf6b307bfd 100644
--- a/init/main.c
+++ b/init/main.c
@@ -333,6 +333,7 @@ static void __init setup_per_cpu_areas(void)
 {
         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(void)
         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 */