On Fri 21-08-20 08:39:37, Qian Cai wrote: > On Fri, Aug 21, 2020 at 10:01:27AM +0200, Michal Hocko wrote: > > On Thu 20-08-20 10:58:51, Qian Cai wrote: > > > On Tue, Aug 11, 2020 at 07:10:27PM +0800, Alex Shi wrote: > > > > Since readahead page is charged on memcg too, in theory we don't have to > > > > check this exception now. Before safely remove them all, add a warning > > > > for the unexpected !memcg. > > > > > > > > Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> > > > > Acked-by: Michal Hocko <mhocko@xxxxxxxx> > > > > > > This will trigger, > > > > Thanks for the report! > > > > > [ 1863.916499] LTP: starting move_pages12 > > > [ 1863.946520] page:000000008ccc1062 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1fd3c0 > > > [ 1863.946553] head:000000008ccc1062 order:5 compound_mapcount:0 compound_pincount:0 > > > > Hmm, this is really unexpected. How did we get order-5 page here? Is > > this some special mappaing that sys_move_pages should just ignore? > > Well, I thought everybody should be able to figure out where to find the LTP > tests source code at this stage to see what it does. Anyway, the test simply > migrate hugepages while soft offlining, so order 5 is expected as that is 2M > hugepage on powerpc (also reproduced on x86 below). It might be easier to > reproduce using our linux-mm random bug collection on NUMA systems. OK, I must have missed that this was on ppc. The order makes more sense now. I will have a look at this next week. Thanks! -- Michal Hocko SUSE Labs
