Lucid SRU, CONFIG_NR_CPUS=256, LP706058

[Tim Gardner]

The following changes since commit b09a4b6f2843b58a420fa6b75c991c1ed5defe92:
  Greg Kroah-Hartman (1):
        Linux 2.6.32.28

are available in the git repository at:

  git://kernel.ubuntu.com/rtg/ubuntu-lucid.git nr_cpus_256_lp706058

Tim Gardner (1):
      UBUNTU: [Config] Set CONFIG_NR_CPUS=256 for amd64 server

 debian.master/config/amd64/config.common.amd64    |    1 -
 debian.master/config/amd64/config.flavour.generic |    1 +
 debian.master/config/amd64/config.flavour.preempt |    1 +
 debian.master/config/amd64/config.flavour.server  |    1 +
 4 files changed, 3 insertions(+), 1 deletions(-)

>From 5d57615ee98ce183935a373c5750b14c32f2d877 Mon Sep 17 00:00:00 2001
From: Tim Gardner <tim.gardner at canonical.com>
Date: Fri, 21 Jan 2011 13:05:17 -0700
Subject: [PATCH] UBUNTU: [Config] Set CONFIG_NR_CPUS=256 for amd64 server

BugLink: http://bugs.launchpad.net/bugs/706058

The CPU hotplug subsytem allocates memory using the per-cpu mechanism. Enough
memory is pre-defined by CONFIG_NR_CPUS to accommodate the maximum number of
CPUs that can be online. This value is discovered at boot time and is used to
trim the actual memory allocated to the real number of CPUs. In effect,
CONFIG_NR_CPUS has little impact on memory consumption except for these 9 vairables:

kernel/cpu.c:static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
kernel/cpu.c:static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
kernel/cpu.c:static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
kernel/cpu.c:static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
kernel/cpu.c:static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
kernel/sched.c: DECLARE_BITMAP(cpus, CONFIG_NR_CPUS);
kernel/sched.c: DECLARE_BITMAP(span, CONFIG_NR_CPUS);
kernel/sched.c: static DECLARE_BITMAP(tmpmask, CONFIG_NR_CPUS);
mm/slub.c:static DECLARE_BITMAP(kmem_cach_cpu_free_init_once, CONFIG_NR_CPUS);

The increase in memory size of these variables is negligible since they are bit
map structures. For example, increasing from 64 to 256 only adds 24 bytes per
variable.

Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 debian.master/config/amd64/config.common.amd64    |    1 -
 debian.master/config/amd64/config.flavour.generic |    1 +
 debian.master/config/amd64/config.flavour.preempt |    1 +
 debian.master/config/amd64/config.flavour.server  |    1 +
 4 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/debian.master/config/amd64/config.common.amd64 b/debian.master/config/amd64/config.common.amd64
index f2352c8..cd2cc3a 100644
--- a/debian.master/config/amd64/config.common.amd64
+++ b/debian.master/config/amd64/config.common.amd64
@@ -97,7 +97,6 @@ CONFIG_MTD_SLRAM=m
 CONFIG_NDISWRAPPER=m
 CONFIG_NFTL=m
 CONFIG_NO_HZ=y
-CONFIG_NR_CPUS=64
 CONFIG_OUTPUT_FORMAT="elf64-x86-64"
 CONFIG_PARPORT=m
 CONFIG_PCCARD=m
diff --git a/debian.master/config/amd64/config.flavour.generic b/debian.master/config/amd64/config.flavour.generic
index 650ae59..89668a2 100644
--- a/debian.master/config/amd64/config.flavour.generic
+++ b/debian.master/config/amd64/config.flavour.generic
@@ -8,6 +8,7 @@ CONFIG_HZ=100
 CONFIG_HZ_100=y
 # CONFIG_HZ_1000 is not set
 # CONFIG_MEMORY_HOTPLUG is not set
+CONFIG_NR_CPUS=64
 # CONFIG_PREEMPT is not set
 # CONFIG_PREEMPT_NONE is not set
 CONFIG_PREEMPT_VOLUNTARY=y
diff --git a/debian.master/config/amd64/config.flavour.preempt b/debian.master/config/amd64/config.flavour.preempt
index becca6f..968f1eb 100644
--- a/debian.master/config/amd64/config.flavour.preempt
+++ b/debian.master/config/amd64/config.flavour.preempt
@@ -8,6 +8,7 @@ CONFIG_HZ=1000
 # CONFIG_HZ_100 is not set
 CONFIG_HZ_1000=y
 # CONFIG_MEMORY_HOTPLUG is not set
+CONFIG_NR_CPUS=64
 CONFIG_PREEMPT=y
 # CONFIG_PREEMPT_NONE is not set
 # CONFIG_PREEMPT_VOLUNTARY is not set
diff --git a/debian.master/config/amd64/config.flavour.server b/debian.master/config/amd64/config.flavour.server
index 8d734fb..75fcc3e 100644
--- a/debian.master/config/amd64/config.flavour.server
+++ b/debian.master/config/amd64/config.flavour.server
@@ -8,6 +8,7 @@ CONFIG_HZ=100
 CONFIG_HZ_100=y
 # CONFIG_HZ_1000 is not set
 CONFIG_MEMORY_HOTPLUG=y
+CONFIG_NR_CPUS=256
 # CONFIG_PREEMPT is not set
 CONFIG_PREEMPT_NONE=y
 # CONFIG_PREEMPT_VOLUNTARY is not set
-- 
1.7.0.4