mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y
authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Fri, 29 Sep 2017 14:08:16 +0000 (17:08 +0300)
committerIngo Molnar <mingo@kernel.org>
Fri, 20 Oct 2017 11:07:09 +0000 (13:07 +0200)
commit83e3c48729d9ebb7af5a31a504f3fd6aff0348c4
tree9e42ac40f3bb837359325e0b247ec8e16c1c0b52
parent967535223f9a8d95c187a8728480b569164cd4f4
mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y

Size of the mem_section[] array depends on the size of the physical address space.

In preparation for boot-time switching between paging modes on x86-64
we need to make the allocation of mem_section[] dynamic, because otherwise
we waste a lot of RAM: with CONFIG_NODE_SHIFT=10, mem_section[] size is 32kB
for 4-level paging and 2MB for 5-level paging mode.

The patch allocates the array on the first call to sparse_memory_present_with_active_regions().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@suse.de>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170929140821.37654-2-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
include/linux/mmzone.h
mm/page_alloc.c
mm/sparse.c