>-----Original Message----- >From: Joonsoo Kim [mailto:iamjoonsoo.kim@xxxxxxx] >Sent: 2014年7月7日 12:54 >To: Lisa Du >Cc: linux-mm@xxxxxxxxx >Subject: Re: NR_FREE_CMA_PAGES larger than total CMA size > >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. :) Below patches works for me, thanks a lot! mm/page_alloc: handle page on pcp correctly if it's pageblock is isolated mm/page_alloc: carefully free the page on isolate pageblock > >Thanks. ?韬{.n???檩jg???a?旃???)钋???骅w+h?璀?ｙ/i?⒏??⒎???Щ ??m?? ?)钋???痂?^??觥??ザ?v???O璁?f??i?⒏?