Re: [PATCH] mm: setup pageblock_order before it's used by sparse
From: Mel Gorman <mgorman@suse.de>
Date: 2012-07-02 12:41:11
Also in:
lkml, stable
On Sat, Jun 30, 2012 at 05:07:54PM +0800, Jiang Liu wrote:
From: Xishi Qiu <redacted>
On architectures with CONFIG_HUGETLB_PAGE_SIZE_VARIABLE set, such as Itanium,
pageblock_order is a variable with default value of 0. It's set to the right
value by set_pageblock_order() in function free_area_init_core().
But pageblock_order may be used by sparse_init() before free_area_init_core()
is called along path:
sparse_init()
->sparse_early_usemaps_alloc_node()
->usemap_size()
->SECTION_BLOCKFLAGS_BITS
->((1UL << (PFN_SECTION_SHIFT - pageblock_order)) *
NR_PAGEBLOCK_BITS)
The uninitialized pageblock_size will cause memory wasting because usemap_size()
returns a much bigger value then it's really needed.
For example, on an Itanium platform,
sparse_init() pageblock_order=0 usemap_size=24576
free_area_init_core() before pageblock_order=0, usemap_size=24576
free_area_init_core() after pageblock_order=12, usemap_size=8
That means 24K memory has been wasted for each section, so fix it by calling
set_pageblock_order() from sparse_init().
Signed-off-by: Xishi Qiu <redacted>
Signed-off-by: Jiang Liu <redacted>Looks all right. Acked-by: Mel Gorman <mgorman@suse.de> This should be considered a stable candidate. Add Cc: stable <redacted> above your Signed-off-by and it'll get picked up if the patch is merged to mainline. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>