Messages in this thread | | | Date | Sat, 12 Oct 2019 12:30:48 +0200 | From | osalvador <> | Subject | Re: memory offline infinite loop after soft offline |
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On 2019-10-11 23:32, Qian Cai wrote: > # /opt/ltp/runtest/bin/move_pages12 > move_pages12.c:263: INFO: Free RAM 258988928 kB > move_pages12.c:281: INFO: Increasing 2048kB hugepages pool on node 0 to > 4 > move_pages12.c:291: INFO: Increasing 2048kB hugepages pool on node 8 to > 4 > move_pages12.c:207: INFO: Allocating and freeing 4 hugepages on node 0 > move_pages12.c:207: INFO: Allocating and freeing 4 hugepages on node 8 > move_pages12.c:197: PASS: Bug not reproduced > move_pages12.c:197: PASS: Bug not reproduced > > for mem in $(ls -d /sys/devices/system/memory/memory*); do > echo offline > $mem/state > echo online > $mem/state > done > > That LTP move_pages12 test will first madvise(MADV_SOFT_OFFLINE) for a > range. > Then, one of "echo offline" will trigger an infinite loop in > __offline_pages() > here,
I did not deeply check whether this issue is really related soft-offline.
As is, soft-offline has a few issues that can lead to tricky problems. Actually, lately I have received quite a few reports from customers where testing soft-offline resulted in applications crashing all around.
I am working on a re-implementation to fix those issues [1]. I yet have to fix a bug I found yesterday though, but it should be quite trivial to fix it up, so I should be able to send a new re-spin next week.
[1] https://lore.kernel.org/patchwork/cover/1126173/
Thanks
> > /* check again */ > ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn, > NULL, check_pages_isolated_cb); > } while (ret); > > because check_pages_isolated_cb() always return -EBUSY from > test_pages_isolated(), > > > pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, > skip_hwpoisoned_pages); > ... > return pfn < end_pfn ? -EBUSY : 0; > > The root cause is in __test_page_isolated_in_pageblock() where "pfn" is > always > less than "end_pfn" because the associated page is not a PageBuddy. > > while (pfn < end_pfn) { > ... > else > break; > > return pfn; > > Adding a dump_page() for that pfn shows, > > [ 101.665160][ T8885] pfn = 77501, end_pfn = 78000 > [ 101.665245][ T8885] page:c00c000001dd4040 refcount:0 mapcount:0 > mapping:0000000000000000 index:0x0 > [ 101.665329][ T8885] flags: 0x3fffc000000000() > [ 101.665391][ T8885] raw: 003fffc000000000 0000000000000000 > ffffffff01dd0500 > 0000000000000000 > [ 101.665498][ T8885] raw: 0000000000000000 0000000000000000 > 00000000ffffffff > 0000000000000000 > [ 101.665588][ T8885] page dumped because: soft_offline > [ 101.665639][ T8885] page_owner tracks the page as freed > [ 101.665697][ T8885] page last allocated via order 5, migratetype > Movable, > gfp_mask > 0x346cca(GFP_HIGHUSER_MOVABLE|__GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_COMP|__GFP_ > THISNODE) > [ 101.665924][ T8885] prep_new_page+0x3c0/0x440 > [ 101.665962][ T8885] get_page_from_freelist+0x2568/0x2bb0 > [ 101.666059][ T8885] __alloc_pages_nodemask+0x1b4/0x670 > [ 101.666115][ T8885] alloc_fresh_huge_page+0x244/0x6e0 > [ 101.666183][ T8885] alloc_migrate_huge_page+0x30/0x70 > [ 101.666254][ T8885] alloc_new_node_page+0xc4/0x380 > [ 101.666325][ T8885] migrate_pages+0x3b4/0x19e0 > [ 101.666375][ T8885] do_move_pages_to_node.isra.29.part.30+0x44/0xa0 > [ 101.666464][ T8885] kernel_move_pages+0x498/0xfc0 > [ 101.666520][ T8885] sys_move_pages+0x28/0x40 > [ 101.666643][ T8885] system_call+0x5c/0x68 > [ 101.666665][ T8885] page last free stack trace: > [ 101.666704][ T8885] __free_pages_ok+0xa4c/0xd40 > [ 101.666773][ T8885] update_and_free_page+0x2dc/0x5b0 > [ 101.666821][ T8885] free_huge_page+0x2dc/0x740 > [ 101.666875][ T8885] __put_compound_page+0x64/0xc0 > [ 101.666926][ T8885] putback_active_hugepage+0x228/0x390 > [ 101.666990][ T8885] migrate_pages+0xa78/0x19e0 > [ 101.667048][ T8885] soft_offline_page+0x314/0x1050 > [ 101.667117][ T8885] sys_madvise+0x1068/0x1080 > [ 101.667185][ T8885] system_call+0x5c/0x68
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