On 2016/3/7 12:34, Joonsoo Kim wrote: > On Fri, Mar 04, 2016 at 03:35:26PM +0800, Hanjun Guo wrote: >> On 2016/3/4 14:38, Joonsoo Kim wrote: >>> On Fri, Mar 04, 2016 at 02:05:09PM +0800, Hanjun Guo wrote: >>>> On 2016/3/4 12:32, Joonsoo Kim wrote: >>>>> On Fri, Mar 04, 2016 at 11:02:33AM +0900, Joonsoo Kim wrote: >>>>>> On Thu, Mar 03, 2016 at 08:49:01PM +0800, Hanjun Guo wrote: >>>>>>> On 2016/3/3 15:42, Joonsoo Kim wrote: >>>>>>>> 2016-03-03 10:25 GMT+09:00 Laura Abbott <labb...@redhat.com>: >>>>>>>>> (cc -mm and Joonsoo Kim) >>>>>>>>> >>>>>>>>> >>>>>>>>> On 03/02/2016 05:52 AM, Hanjun Guo wrote: >>>>>>>>>> Hi, >>>>>>>>>> >>>>>>>>>> I came across a suspicious error for CMA stress test: >>>>>>>>>> >>>>>>>>>> Before the test, I got: >>>>>>>>>> -bash-4.3# cat /proc/meminfo | grep Cma >>>>>>>>>> CmaTotal: 204800 kB >>>>>>>>>> CmaFree: 195044 kB >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> After running the test: >>>>>>>>>> -bash-4.3# cat /proc/meminfo | grep Cma >>>>>>>>>> CmaTotal: 204800 kB >>>>>>>>>> CmaFree: 6602584 kB >>>>>>>>>> >>>>>>>>>> So the freed CMA memory is more than total.. >>>>>>>>>> >>>>>>>>>> Also the the MemFree is more than mem total: >>>>>>>>>> >>>>>>>>>> -bash-4.3# cat /proc/meminfo >>>>>>>>>> MemTotal: 16342016 kB >>>>>>>>>> MemFree: 22367268 kB >>>>>>>>>> MemAvailable: 22370528 kB >>>>>>> [...] >>>>>>>>> I played with this a bit and can see the same problem. The sanity >>>>>>>>> check of CmaFree < CmaTotal generally triggers in >>>>>>>>> __move_zone_freepage_state in unset_migratetype_isolate. >>>>>>>>> This also seems to be present as far back as v4.0 which was the >>>>>>>>> first version to have the updated accounting from Joonsoo. >>>>>>>>> Were there known limitations with the new freepage accounting, >>>>>>>>> Joonsoo? >>>>>>>> I don't know. I also played with this and looks like there is >>>>>>>> accounting problem, however, for my case, number of free page is >>>>>>>> slightly less >>>>>>>> than total. I will take a look. >>>>>>>> >>>>>>>> Hanjun, could you tell me your malloc_size? I tested with 1 and it >>>>>>>> doesn't >>>>>>>> look like your case. >>>>>>> I tested with malloc_size with 2M, and it grows much bigger than 1M, >>>>>>> also I >>>>>>> did some other test: >>>>>> Thanks! Now, I can re-generate erronous situation you mentioned. >>>>>> >>>>>>> - run with single thread with 100000 times, everything is fine. >>>>>>> >>>>>>> - I hack the cam_alloc() and free as below [1] to see if it's lock >>>>>>> issue, with >>>>>>> the same test with 100 multi-thread, then I got: >>>>>> [1] would not be sufficient to close this race. >>>>>> >>>>>> Try following things [A]. And, for more accurate test, I changed code a >>>>>> bit more >>>>>> to prevent kernel page allocation from cma area [B]. This will prevent >>>>>> kernel >>>>>> page allocation from cma area completely so we can focus >>>>>> cma_alloc/release race. >>>>>> >>>>>> Although, this is not correct fix, it could help that we can guess >>>>>> where the problem is. >>>>> More correct fix is something like below. >>>>> Please test it. >>>> Hmm, this is not working: >>> 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! > > 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.
Hi, Hanjun Guo has gone to Tailand on business, so I help him to run this patch. The result shows that the count of "CmaFree:" is OK now. But sometimes printed some information as below: alloc_contig_range: [28500, 28600) PFNs busy alloc_contig_range: [28300, 28380) PFNs busy > > Thanks. > > ---------->8------------- >>From dd41e348572948d70b935fc24f82c096ff0fb417 Mon Sep 17 00:00:00 2001 > From: Joonsoo Kim <iamjoonsoo....@lge.com> > Date: Fri, 4 Mar 2016 13:28:17 +0900 > Subject: [PATCH] mm/cma: fix race > > Signed-off-by: Joonsoo Kim <iamjoonsoo....@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; >