Messages in this thread | | | Date | Thu, 14 May 2015 08:48:48 -0700 | Subject | Re: mm: BUG_ON with NUMA_BALANCING (kernel BUG at include/linux/swapops.h:131!) | From | Haren Myneni <> |
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On 5/14/15, Mel Gorman <mgorman@suse.de> wrote: > On Wed, May 13, 2015 at 01:17:54AM -0700, Haren Myneni wrote: >> Hi, >> >> I am getting BUG_ON in migration_entry_to_page() with 4.1.0-rc2 >> kernel on powerpc system which has 512 CPUs (64 cores - 16 nodes) and >> 1.6 TB memory. We can easily recreate this issue with kernel compile >> (make -j500). But I could not reproduce with numa_balancing=disable. >> > > Is this patched in any way? I ask because line 134 on 4.1.0-rc2 does not > match up with a BUG_ON. It's close to a PageLocked check but I want to > be sure there are no other modifications.
Mel, Thanks for your help. I added some printks and dump_page() to get the page struct and swp_entry information.
> > Otherwise, when was the last time this worked? Was 4.0 ok? As it can be > easily reproduced, can the problem be bisected please?
I did not try previous versions other than RHEL kernel (3.10.*). I will try with previous versions.
In the failure case, also noticed pte and address values are matched in try_to_unmap_one() and remove_migration_pte(), but entry (swp_entry_t) value is different. So looks like page strut address in migration_entry_to_page() is not valid.
try_to_unmap_one() {
... } else if (IS_ENABLED(CONFIG_MIGRATION)) { /* * Store the pfn of the page in a special migration * pte. do_swap_page() will wait until the migration * pte is removed and then restart fault handling. */ BUG_ON(!(flags & TTU_MIGRATION)); entry = make_migration_entry(page, pte_write(pteval)); } swp_pte = swp_entry_to_pte(entry); if (pte_soft_dirty(pteval)) swp_pte = pte_swp_mksoft_dirty(swp_pte); set_pte_at(mm, address, pte, swp_pte);
/*pte=0xb16b8d0f80000000 address=0x100008150000 page=0xf000000513f3e1e0 entry=0x3e0000000ec5ae34 */ ... }
remove_migration_pte() { ... /* address=0x100008150000 pte=0xb16b8d0f80000000 *old=0xf000000513f3e1e0 */ if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old) goto unlock; ... }
migration_entry_to_page() { pte=0xb16b8d0f80000000 entry=0x3e00000002c5ae34 page=0xf0000000f3f3e1e0 }
Thanks Haren
> > -- > Mel Gorman > SUSE Labs >
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