On 2012-7-3 4:43, Yinghai Lu wrote: > On Sun, Jul 1, 2012 at 7:01 PM, Jiang Liu <jiang.liu@xxxxxxxxxx> wrote: >> Hi Yinghai, >> The patch fails compilation as below: >> mm/page_alloc.c:151: error: initializer element is not constant >> mm/page_alloc.c:151: error: expected ‘,’ or ‘;’ before ‘__attribute__’ >> >> On IA64, HUGETLB_PAGE_ORDER has dependency on variable hpage_shift. >> # define HUGETLB_PAGE_ORDER (HPAGE_SHIFT - PAGE_SHIFT) >> # define HPAGE_SHIFT hpage_shift >> >> And hpage_shift could be changed by early parameter "hugepagesz". >> So seems will still need to keep function set_pageblock_order(). > > ah, then use use _DEFAULT instead and later could update that in earlyparam. > > So attached -v2 should work. Hi Yinghai, I'm afraid the v2 will break powerpc. Currently only IA64 and PowerPC supports variable hugetlb size. HPAGE_SHIFT is a variable default to 0 on powerpc. But seems PowerPC is doing something wrong here, according to it's mm initialization sequence as below: start_kernel() setup_arch() paging_init() free_area_init_node() set_pageblock_order() refer to HPAGE_SHIFT (still 0) init_rest() do_initcalls() hugetlbpage_init() setup HPAGE_SHIFT That means pageblock_order is always set to "MAX_ORDER - 1", not sure whether this is intended. And it has the same issue as IA64 of wasting memory if CONFIG_SPARSE is enabled. So it would be better to keep function set_pageblock_order(), it will fix the memory wasting on both IA64 and PowerPC. Thanks! Gerry > > Thanks > > Yinghai -- 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>