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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2008-08-25 14:15:38 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-08-25 14:15:38 -0700 |
| commit | d25e26b61d59370eee8b7f2634641eb0fa76e952 (patch) | |
| tree | 51356ee7102416d8f61a55b8447e7f59279347f5 /arch | |
| parent | 426e1eafdbd1d1349c852a2b90c7f20879d52ed2 (diff) | |
| download | linux-d25e26b61d59370eee8b7f2634641eb0fa76e952.tar.gz linux-d25e26b61d59370eee8b7f2634641eb0fa76e952.tar.bz2 linux-d25e26b61d59370eee8b7f2634641eb0fa76e952.zip | |
[x86] Clean up MAXSMP Kconfig, and limit NR_CPUS to 512
This fixes a regression that was indirectly caused by commit
1184dc2ffe2c8fb9afb766d870850f2c3165ef25 ("x86: modify Kconfig to allow
up to 4096 cpus").
Allowing 4k CPU's is not practical at this time, because we still have a
number of places that have several 'cpumask_t's on the stack, and a
4k-bit cpumask is 512 bytes of stack-space for each such variable. This
literally caused functions like 'smp_call_function_mask' to have a 2.5kB
stack frame, and several functions to have 2kB stackframes.
With an 8kB stack total, smashing the stack was simply much too likely.
At least bugzilla entry
http://bugzilla.kernel.org/show_bug.cgi?id=11342
was due to this.
The earlier commit to not inline load_module() into sys_init_module()
fixed the particular symptoms of this that Alan Brunelle saw in that
bugzilla entry, but the huge stack waste by cpumask_t's was the more
direct cause.
Some day we'll have allocation helpers that allocate large CPU masks
dynamically, but in the meantime we simply cannot allow cpumasks this
large.
Cc: Alan D. Brunelle <Alan.Brunelle@hp.com>
Cc: Mike Travis <travis@sgi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/Kconfig | 30 |
1 files changed, 8 insertions, 22 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 68d91c8233f4..ed92864d1325 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -577,35 +577,29 @@ config SWIOTLB config IOMMU_HELPER def_bool (CALGARY_IOMMU || GART_IOMMU || SWIOTLB || AMD_IOMMU) + config MAXSMP bool "Configure Maximum number of SMP Processors and NUMA Nodes" - depends on X86_64 && SMP + depends on X86_64 && SMP && BROKEN default n help Configure maximum number of CPUS and NUMA Nodes for this architecture. If unsure, say N. -if MAXSMP -config NR_CPUS - int - default "4096" -endif - -if !MAXSMP config NR_CPUS - int "Maximum number of CPUs (2-4096)" - range 2 4096 + int "Maximum number of CPUs (2-512)" if !MAXSMP + range 2 512 depends on SMP + default "4096" if MAXSMP default "32" if X86_NUMAQ || X86_SUMMIT || X86_BIGSMP || X86_ES7000 default "8" help This allows you to specify the maximum number of CPUs which this - kernel will support. The maximum supported value is 4096 and the + kernel will support. The maximum supported value is 512 and the minimum value which makes sense is 2. This is purely to save memory - each supported CPU adds approximately eight kilobytes to the kernel image. -endif config SCHED_SMT bool "SMT (Hyperthreading) scheduler support" @@ -996,17 +990,10 @@ config NUMA_EMU into virtual nodes when booted with "numa=fake=N", where N is the number of nodes. This is only useful for debugging. -if MAXSMP - config NODES_SHIFT - int - default "9" -endif - -if !MAXSMP -config NODES_SHIFT - int "Maximum NUMA Nodes (as a power of 2)" + int "Maximum NUMA Nodes (as a power of 2)" if !MAXSMP range 1 9 if X86_64 + default "9" if MAXSMP default "6" if X86_64 default "4" if X86_NUMAQ default "3" @@ -1014,7 +1001,6 @@ config NODES_SHIFT help Specify the maximum number of NUMA Nodes available on the target system. Increases memory reserved to accomodate various tables. -endif config HAVE_ARCH_BOOTMEM_NODE def_bool y |