On Tue 01-12-15 22:34:55, Minchan Kim wrote: > With new test on mmotm-2015-11-25-17-08, I saw below WARNING message > several times. I couldn't see it with reverting new THP refcount > redesign. Just a wild guess. What prevents migration/compaction from calling split_huge_page on thp zero page? There is VM_BUG_ON but it is not clear whether you run with CONFIG_DEBUG_VM enabled. Also, how big is the underflow? > I will try to make reproducer when I have a time but not sure. > Before that, I hope someone catches it up. > > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 1340 at mm/page_counter.c:26 page_counter_cancel+0x34/0x40() > Modules linked in: > CPU: 0 PID: 1340 Comm: madvise_test Not tainted 4.4.0-rc2-mm1-kirill+ #12 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > ffffffff81782eeb ffff880072b97be8 ffffffff8126f476 0000000000000000 > ffff880072b97c20 ffffffff8103e476 ffff88006b35d0b0 00000000000001fe > 0000000000000000 00000000000001fe ffff88006b35d000 ffff880072b97c30 > Call Trace: > [<ffffffff8126f476>] dump_stack+0x44/0x5e > [<ffffffff8103e476>] warn_slowpath_common+0x86/0xc0 > [<ffffffff8103e56a>] warn_slowpath_null+0x1a/0x20 > [<ffffffff8114c754>] page_counter_cancel+0x34/0x40 > [<ffffffff8114c852>] page_counter_uncharge+0x22/0x30 > [<ffffffff8114fe17>] uncharge_batch+0x47/0x140 > [<ffffffff81150033>] uncharge_list+0x123/0x190 > [<ffffffff8115222b>] mem_cgroup_uncharge_list+0x1b/0x20 > [<ffffffff810fe9bb>] release_pages+0xdb/0x350 > [<ffffffff8113044d>] free_pages_and_swap_cache+0x9d/0x120 > [<ffffffff8111a546>] tlb_flush_mmu_free+0x36/0x60 > [<ffffffff8111b63c>] tlb_finish_mmu+0x1c/0x50 > [<ffffffff81125f38>] exit_mmap+0xd8/0x130 > [<ffffffff8103bd56>] mmput+0x56/0xe0 > [<ffffffff8103ff4d>] do_exit+0x1fd/0xaa0 > [<ffffffff8104086f>] do_group_exit+0x3f/0xb0 > [<ffffffff810408f4>] SyS_exit_group+0x14/0x20 > [<ffffffff8142b617>] entry_SYSCALL_64_fastpath+0x12/0x6a > ---[ end trace 7864cf719fb83e12 ]--- -- Michal Hocko SUSE Labs -- 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>