Do not depend on MAX_ORDER when grouping pages by mobility

Currently mobility grouping works at the MAX_ORDER_NR_PAGES level.  This makes
sense for the majority of users where this is also the huge page size.
However, on platforms like ia64 where the huge page size is runtime
configurable it is desirable to group at a lower order.  On x86_64 and
occasionally on x86, the hugepage size may not always be MAX_ORDER_NR_PAGES.

This patch groups pages together based on the value of HUGETLB_PAGE_ORDER.  It
uses a compile-time constant if possible and a variable where the huge page
size is runtime configurable.

It is assumed that grouping should be done at the lowest sensible order and
that the user would not want to override this.  If this is not true,
page_block order could be forced to a variable initialised via a boot-time
kernel parameter.

One potential issue with this patch is that IA64 now parses hugepagesz with
early_param() instead of __setup().  __setup() is called after the memory
allocator has been initialised and the pageblock bitmaps already setup.  In
tests on one IA64 there did not seem to be any problem with using
early_param() and in fact may be more correct as it guarantees the parameter
is handled before the parsing of hugepages=.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Andy Whitcroft <apw@shadowen.org>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 7 insertions, 2 deletions

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 802b082e216d..f80f5e2aec87 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -54,6 +54,11 @@ config ARCH_HAS_ILOG2_U64
         bool
         default n
 
+config HUGETLB_PAGE_SIZE_VARIABLE
+        bool
+        depends on HUGETLB_PAGE
+        default y
+
 config GENERIC_FIND_NEXT_BIT
         bool
         default y
diff --git a/arch/ia64/mm/hugetlbpage.c b/arch/ia64/mm/hugetlbpage.c
index a9ff685aea25..d3ce8f3bcaa6 100644
--- a/arch/ia64/mm/hugetlbpage.c
+++ b/arch/ia64/mm/hugetlbpage.c
@@ -194,6 +194,6 @@ static int __init hugetlb_setup_sz(char *str)
          * override here with new page shift.
          */
         ia64_set_rr(HPAGE_REGION_BASE, hpage_shift << 2);
-        return 1;
+        return 0;
 }
-__setup("hugepagesz=", hugetlb_setup_sz);
+early_param("hugepagesz", hugetlb_setup_sz);