[rfc git pull] cpus4096 fixes, take 2

[Ingo Molnar]

* Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> > But I'll redo the patch again.
> 
> Here's a trivial setup, that is even tested. It's _small_ too.
> 
> 	/* cpu_bit_bitmap[0] is empty - so we can back into it */
> 	#define MASK_DECLARE_1(x) [x+1][0] = 1ul << (x)
> 	#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
> 	#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
> 	#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
> 
> 	static const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
> 		MASK_DECLARE_8(0), MASK_DECLARE_8(8),
> 		MASK_DECLARE_8(16), MASK_DECLARE_8(24),
> 	#if BITS_PER_LONG > 32
> 		MASK_DECLARE_8(32), MASK_DECLARE_8(40),
> 		MASK_DECLARE_8(48), MASK_DECLARE_8(56),
> 	#endif
> 	};
> 
> 	static inline const cpumask_t *get_cpu_mask(unsigned int nr)
> 	{
> 		const unsigned long *p = cpu_bit_bitmap[1 + nr % BITS_PER_LONG];
> 		p -= nr / BITS_PER_LONG;
> 		return (const cpumask_t *)p;
> 	}
> 
> that should be all you need to do.
> 
> Honesty in advertizing: my "testing" was some trivial user-space 
> harness, maybe I had some bug in it. But at least it's not _horribly_ 
> wrong.

Amazing! Your code, once plugged into the kernel proper, booted fine on 
5 different x86 testsystems, it booted fine an allyesconfig kernel with 
MAXSMP and NR_CPUS=4096, it booted fine on allnoconfig as well (and 
allmodconfig and on a good number of randconfigs as well).

> And yes, this has the added optimization from Viro of overlapping the 
> cpumask_t's internally too, rather than making them twice the size. So 
> with 4096 CPU's, this should result 32.5kB of static const data.

What do you think about the commit below?

I've put your fix into:

  # e56b3bc: cpu masks: optimize and clean up cpumask_of_cpu()

It's quoted fully below after the pull request diffstat. Have i missed 
anything obvious?

What i'm unsure about are other architectures. (Small detail i just 
noticed: HAVE_CPUMASK_OF_CPU_MAP is now orphaned in arch/x86/Kconfig, 
will get rid of that in a separate change, i dont want to upset the test 
results.)

( And ... because v1 of your code was so frustratingly and
  mind-blowingly stable in testing (breaking a long track record of v1 
  patches in this area of kernel), and because the perfect patch does 
  not exist by definition, i thought i'd mention that after a long 
  search i found and fixed a serious showstopper bug in your code: you 
  used "1ul" in your macros, instead of the more proper "1UL" style. The
  ratio between the use of 1ul versus 1UL is 1:30 in the tree, so your 
  choice of integer literals type suffix capitalization was deemed 
  un-Linuxish, and was fixed up for good. )

	Ingo

---------------->
Linus,

Please pull the latest cpus4096 git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git cpus4096

 Thanks,

	Ingo

------------------>
Ingo Molnar (1):
      cpumask: export cpumask_of_cpu_map

Linus Torvalds (1):
      cpu masks: optimize and clean up cpumask_of_cpu()

Mike Travis (3):
      cpumask: make cpumask_of_cpu_map generic
      cpumask: put cpumask_of_cpu_map in the initdata section
      cpumask: change cpumask_of_cpu_ptr to use new cpumask_of_cpu


 arch/x86/kernel/acpi/cstate.c                    |    3 +-
 arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c       |   10 +---
 arch/x86/kernel/cpu/cpufreq/powernow-k8.c        |   15 ++----
 arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c |   12 ++---
 arch/x86/kernel/cpu/cpufreq/speedstep-ich.c      |    3 +-
 arch/x86/kernel/cpu/intel_cacheinfo.c            |    3 +-
 arch/x86/kernel/ldt.c                            |    6 +--
 arch/x86/kernel/microcode.c                      |   17 ++----
 arch/x86/kernel/reboot.c                         |   11 +---
 arch/x86/kernel/setup_percpu.c                   |   21 -------
 drivers/acpi/processor_throttling.c              |   11 +---
 drivers/firmware/dcdbas.c                        |    3 +-
 drivers/misc/sgi-xp/xpc_main.c                   |    3 +-
 include/linux/cpumask.h                          |   63 ++++++++-------------
 kernel/cpu.c                                     |   25 +++++++++
 kernel/stop_machine.c                            |    3 +-
 kernel/time/tick-common.c                        |    8 +--
 kernel/trace/trace_sysprof.c                     |    4 +-
 lib/smp_processor_id.c                           |    5 +--
 net/sunrpc/svc.c                                 |    3 +-
 20 files changed, 86 insertions(+), 143 deletions(-)

---->

  # e56b3bc: cpu masks: optimize and clean up cpumask_of_cpu()