On Sat, Jul 05, 2014 at 01:13:17AM -0700, Lisa Du wrote: > Dear Sir > Recently I met one issue that after system run for a long time, free cma pages recorded > in vm_stat[NR_FREE_CMA_PAGES] are larger than total CMA size declared. > For example, I declared 64MB CMA size, but found free cma was 70MB. > > I added some trace to track how it happen, and found the reason maybe like below: > 1) alloc_contig_range() want to allocate a range [start, end], for example [0x1e040, 0x1e050]; > > 2) start_isolate_page_range() will isolate the range [pfn_max_align_down(start), > pfn_max_align_up(end)]; for this example it's [0x1e000, 0x1e400] (MAX_ORDER is 11); > > 3) drain_all_pages() would be called as follows, if there's some pages belong to the range > [0x1e000, 0x1e400] was freed from the pcp_list, also if the page was MIGRATE_CMA, > then vm_stat[NR_FREE_CMA_PAGES] would increase and also NR_FREE_PAGES; > > 4) if the freed pages in #3 was not the range of [start, end], then at last undo_isolate_page_range() > will be called, and the pages would be calculated again as free pages in unset_migratetype_isolate(), > and __mod_zone_freepage_state() will increased again for these pages for both NR_FREE_CMA_PAGES > and NR_FREE_PAGES. > The function calling flow as below, the free pages in move_freepages() was calculated again. > undo_isolate_page_range() > --> unset_migratetype_isolate() > --> move_freepages_block() > --> move_freepages() > --> __mod_zone_freepage_state() > > Shall we add some check in move_freepages() if the page was already in CMA free list, > then exclude it from the pages_moved? > > I found this issue in kernel v3.4, but seems there's no fix in latest kernel code base. > Not sure if anyone else has met such issue? Anyone would help to comment? Thanks a lot! Hello, Maybe this bug is relevant for my recent patchset. I don't have much time to investigate your problem, so if you have interest on my patchset, please look at it on below link https://lkml.org/lkml/2014/7/4/79 If they work for you, please let me know. :) Thanks. -- 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>