On Mon 23-05-16 09:54:31, Yang Shi wrote:
> Per the suggestion from Michal Hocko [1], CONFIG_DEFERRED_STRUCT_PAGE_INIT
> should be incompatible with FLATMEM, make this explicitly in Kconfig.
I guess the changelog could benefit from some clarification. What
do you think about the following:
"
DEFERRED_STRUCT_PAGE_INIT requires some ordering wrt other
initialization operations, e.g. page_ext_init has to happen after the
whole memmap is initialized properly. For SPARSEMEM this requires to
wait for page_alloc_init_late. Other memory models (e.g. flatmem) might
have different initialization layouts (page_ext_init_flatmem). Currently
DEFERRED_STRUCT_PAGE_INIT depends on MEMORY_HOTPLUG which in turn
depends on SPARSEMEM || X86_64_ACPI_NUMA
depends on ARCH_ENABLE_MEMORY_HOTPLUG
and X86_64_ACPI_NUMA depends on NUMA which in turn disable FLATMEM
memory model:
config ARCH_FLATMEM_ENABLE
def_bool y
depends on X86_32 && !NUMA
so FLATMEM is ruled out via dependency maze. Be explicit and disable
FLATMEM for DEFERRED_STRUCT_PAGE_INIT so that we do not reintroduce
subtle initialization bugs
"
>
> [1] http://lkml.kernel.org/r/[email protected]
>
> Signed-off-by: Yang Shi <[email protected]>
> ---
> mm/Kconfig | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 2664c11..22fa818 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -649,6 +649,7 @@ config DEFERRED_STRUCT_PAGE_INIT
> default n
> depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
> depends on MEMORY_HOTPLUG
> + depends on !FLATMEM
> help
> Ordinarily all struct pages are initialised during early boot in a
> single thread. On very large machines this can take a considerable
> --
> 2.0.2
--
Michal Hocko
SUSE Labs
