On 2016/7/15 6:17, David Rientjes wrote: > On Thu, 14 Jul 2016, Xishi Qiu wrote: > >> alloc_migrate_target() is called from migrate_pages(), and the page >> is always from user space, so we can add __GFP_HIGHMEM directly. >> >> Second, when we offline a node, the new page should alloced from other >> nodes instead of the current node, because re-migrate is a waste of >> time. >> > > alloc_migrate_target() is not only used from memory hotplug, it is also > used for CMA: we won't be isolating PageHuge() pages in > isolate_migratepages_range(), so this would cause a regression where we'd > be migrating memory to a remote NUMA node rather than preferring to > allocate locally. >
> You may find it useful to use the 'private' field of the migrate_pages() > callback to specify the node the page should preferably be migrated to. > OK, I know, I'll rewrite v2. >> Signed-off-by: Xishi Qiu <qiuxi...@huawei.com> >> --- >> mm/page_isolation.c | 16 ++++++---------- >> 1 file changed, 6 insertions(+), 10 deletions(-) >> >> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >> index 612122b..83848dc 100644 >> --- a/mm/page_isolation.c >> +++ b/mm/page_isolation.c >> @@ -282,20 +282,16 @@ int test_pages_isolated(unsigned long start_pfn, >> unsigned long end_pfn, >> struct page *alloc_migrate_target(struct page *page, unsigned long private, >> int **resultp) >> { >> - gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE; >> - >> /* >> - * TODO: allocate a destination hugepage from a nearest neighbor node, >> + * TODO: allocate a destination page from a nearest neighbor node, >> * accordance with memory policy of the user process if possible. For >> * now as a simple work-around, we use the next node for destination. >> */ >> + int nid = next_node_in(page_to_nid(page), node_online_map); >> + >> if (PageHuge(page)) >> return alloc_huge_page_node(page_hstate(compound_head(page)), >> - next_node_in(page_to_nid(page), >> - node_online_map)); >> - >> - if (PageHighMem(page)) >> - gfp_mask |= __GFP_HIGHMEM; >> - >> - return alloc_page(gfp_mask); >> + nid); >> + else >> + return __alloc_pages_node(nid, GFP_HIGHUSER_MOVABLE, 0); > > I don't think this __alloc_pages_node() does what you think it does, it > only prefers nid here and will readily fallback to other nodes if > necessary. That is different than alloc_huge_page_node() which does no > fallback. So there's two issues with this change: (1) inconsistency > between PageHuge() and !PageHuge() behavior, and (2) the use of > __alloc_pages_node() does not match the commit description which states > "re-migrate is a waste of time." > Yes, you are right, how about change the changelog, one is membind, the other is prefer? Thanks, Xishi Qiu > . >