Messages in this thread | | | Subject | Re: Suspicious error for CMA stress test | From | Vlastimil Babka <> | Date | Mon, 7 Mar 2016 13:59:12 +0100 |
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On 03/07/2016 05:34 AM, Joonsoo Kim wrote: > On Fri, Mar 04, 2016 at 03:35:26PM +0800, Hanjun Guo wrote: >>> Sad to hear that. >>> >>> Could you tell me your system's MAX_ORDER and pageblock_order? >>> >> >> MAX_ORDER is 11, pageblock_order is 9, thanks for your help!
I thought that CMA regions/operations (and isolation IIRC?) were supposed to be MAX_ORDER aligned exactly to prevent needing these extra checks for buddy merging. So what's wrong?
> Hmm... that's same with me. > > Below is similar fix that prevents buddy merging when one of buddy's > migrate type, but, not both, is MIGRATE_ISOLATE. In fact, I have > no idea why previous fix (more correct fix) doesn't work for you. > (It works for me.) But, maybe there is a bug on the fix > so I make new one which is more general form. Please test it. > > Thanks. > > ---------->8------------- > From dd41e348572948d70b935fc24f82c096ff0fb417 Mon Sep 17 00:00:00 2001 > From: Joonsoo Kim <iamjoonsoo.kim@lge.com> > Date: Fri, 4 Mar 2016 13:28:17 +0900 > Subject: [PATCH] mm/cma: fix race > > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> > --- > mm/page_alloc.c | 33 +++++++++++++++++++-------------- > 1 file changed, 19 insertions(+), 14 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index c6c38ed..d80d071 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -620,8 +620,8 @@ static inline void rmv_page_order(struct page *page) > * > * For recording page's order, we use page_private(page). > */ > -static inline int page_is_buddy(struct page *page, struct page *buddy, > - unsigned int order) > +static inline int page_is_buddy(struct zone *zone, struct page *page, > + struct page *buddy, unsigned int order) > { > if (!pfn_valid_within(page_to_pfn(buddy))) > return 0; > @@ -644,6 +644,20 @@ static inline int page_is_buddy(struct page *page, struct page *buddy, > if (page_zone_id(page) != page_zone_id(buddy)) > return 0; > > + if (IS_ENABLED(CONFIG_CMA) && > + unlikely(has_isolate_pageblock(zone)) && > + unlikely(order >= pageblock_order)) { > + int page_mt, buddy_mt; > + > + page_mt = get_pageblock_migratetype(page); > + buddy_mt = get_pageblock_migratetype(buddy); > + > + if (page_mt != buddy_mt && > + (is_migrate_isolate(page_mt) || > + is_migrate_isolate(buddy_mt))) > + return 0; > + } > + > VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy); > > return 1; > @@ -691,17 +705,8 @@ static inline void __free_one_page(struct page *page, > VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page); > > VM_BUG_ON(migratetype == -1); > - if (is_migrate_isolate(migratetype)) { > - /* > - * We restrict max order of merging to prevent merge > - * between freepages on isolate pageblock and normal > - * pageblock. Without this, pageblock isolation > - * could cause incorrect freepage accounting. > - */ > - max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1); > - } else { > + if (!is_migrate_isolate(migratetype)) > __mod_zone_freepage_state(zone, 1 << order, migratetype); > - } > > page_idx = pfn & ((1 << max_order) - 1); > > @@ -711,7 +716,7 @@ static inline void __free_one_page(struct page *page, > while (order < max_order - 1) { > buddy_idx = __find_buddy_index(page_idx, order); > buddy = page + (buddy_idx - page_idx); > - if (!page_is_buddy(page, buddy, order)) > + if (!page_is_buddy(zone, page, buddy, order)) > break; > /* > * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page, > @@ -745,7 +750,7 @@ static inline void __free_one_page(struct page *page, > higher_page = page + (combined_idx - page_idx); > buddy_idx = __find_buddy_index(combined_idx, order + 1); > higher_buddy = higher_page + (buddy_idx - combined_idx); > - if (page_is_buddy(higher_page, higher_buddy, order + 1)) { > + if (page_is_buddy(zone, higher_page, higher_buddy, order + 1)) { > list_add_tail(&page->lru, > &zone->free_area[order].free_list[migratetype]); > goto out; >
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