On Sat, Jun 30, 2012 at 05:07:54PM +0800, Jiang Liu wrote: > From: Xishi Qiu <qiuxishi@xxxxxxxxxx> > > 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 <qiuxishi@xxxxxxxxxx> > Signed-off-by: Jiang Liu <liuj97@xxxxxxxxx> Looks all right. Acked-by: Mel Gorman <mgorman@xxxxxxx> This should be considered a stable candidate. Add Cc: stable <stable@xxxxxxxxxxxxxxx> 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@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>