On Thu, May 28, 2015 at 11:38:36AM -0700, Jovi Zhangwei wrote: > Hi Mel, > > On Thu, May 28, 2015 at 5:00 AM, Mel Gorman <mgorman@xxxxxxx> wrote: > > On Wed, May 27, 2015 at 11:05:33AM -0700, Jovi Zhangwei wrote: > >> Hi, > >> > >> I got below kernel bug error in our 3.18.13 stable kernel. > >> "kernel BUG at mm/migrate.c:1661!" > >> > >> Source code: > >> > >> 1657 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) > >> 1658 { > >> 1659 int page_lru; > >> 1660 > >> 1661 VM_BUG_ON_PAGE(compound_order(page) && > >> !PageTransHuge(page), page); > >> > >> It's easy to trigger the error by run tcpdump in our system.(not sure > >> it will easily be reproduced in another system) > >> "sudo tcpdump -i bond0.100 'tcp port 4242' -c 100000000000 -w 4242.pcap" > >> > >> Any comments for this bug would be great appreciated. thanks. > >> > > > > What sort of compound page is it? What sort of VMA is it in? hugetlbfs > > pages should never be tagged for NUMA migrate and never enter this > > path. Transparent huge pages are handled properly so I'm wondering > > exactly what type of compound page this is and what mapped it into > > userspace. > > > Thanks for your reply. > > After reading net/packet/af_packet.c:alloc_one_pg_vec_page, I found > there indeed have compound page maped into userspace. > Ok, it's clear now. Thanks very much. > I sent a patch for this issue(you may received it), but not sure it's > right to fix, > feel free to update it or use your own patch. > It avoids the problem but it's not the best fix because a lot of useless overhead has been incurred for a page that can never be migrated. Can you try the following instead please? ---8<--- sched, numa: Do not hint for NUMA balancing on VM_MIXEDMAP mappings Jovi Zhangwei reported the following problem Below kernel vm bug can be triggered by tcpdump which mmaped a lot of pages with GFP_COMP flag. [Mon May 25 05:29:33 2015] page:ffffea0015414000 count:66 mapcount:1 mapping: (null) index:0x0 [Mon May 25 05:29:33 2015] flags: 0x20047580004000(head) [Mon May 25 05:29:33 2015] page dumped because: VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page)) [Mon May 25 05:29:33 2015] ------------[ cut here ]------------ [Mon May 25 05:29:33 2015] kernel BUG at mm/migrate.c:1661! [Mon May 25 05:29:33 2015] invalid opcode: 0000 [#1] SMP Compound pages cannot be migrated and it was not expected that such pages be marked for NUMA balancing. This did not take into account that drivers such as net/packet/af_packet.c may insert compound pages into userspace with vm_insert_page. This patch tells the NUMA balancing protection scanner to skip all VM_MIXEDMAP mappings which avoids the possibility that compound pages are marked for migration. Signed-off-by: Mel Gorman <mgorman@xxxxxxx> Reported-by: Jovi Zhangwei <jovi@xxxxxxxxxxxxxx> --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 241213be507c..486d00c408b0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2166,7 +2166,7 @@ void task_numa_work(struct callback_head *work) } for (; vma; vma = vma->vm_next) { if (!vma_migratable(vma) || !vma_policy_mof(vma) || - is_vm_hugetlb_page(vma)) { + is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) { continue; } -- 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>