On Fri 13-10-17 22:42:46, Michael Ellerman wrote: > Vlastimil Babka <vbabka@xxxxxxx> writes: > > On 10/11/2017 08:51 AM, Michal Hocko wrote: > >> On Wed 11-10-17 13:37:50, Michael Ellerman wrote: > >>> Michal Hocko <mhocko@xxxxxxxxxx> writes: > >>>> On Tue 10-10-17 23:05:08, Michael Ellerman wrote: > >>>>> Michal Hocko <mhocko@xxxxxxxxxx> writes: > >>>>>> From: Michal Hocko <mhocko@xxxxxxxx> > >>>>>> > >>>>>> Memory offlining can fail just too eagerly under a heavy memory pressure. > ... > >>>>> > >>>>> This breaks offline for me. > >>>>> > >>>>> Prior to this commit: > >>>>> /sys/devices/system/memory/memory0# time echo 0 > online > >>>>> -bash: echo: write error: Device or resource busy > > > > Well, that means offline didn't actually work for that block even before > > this patch, right? Is it even a movable_node block? I guess not? > > Correct. It should fail. > > >>>>> After: > >>>>> /sys/devices/system/memory/memory0# time echo 0 > online > >>>>> -bash: echo: write error: Device or resource busy > >>>>> > >>>>> real 2m0.009s > >>>>> user 0m0.000s > >>>>> sys 1m25.035s > >>>>> > >>>>> There's no way that block can be removed, it contains the kernel text, > >>>>> so it should instantly fail - which it used to. > > > > Ah, right. So your complain is really about that the failure is not > > instant anymore for blocks that can't be offlined. > > Yes. Previously it failed instantly, now it doesn't fail, and loops > infinitely (once the 2 minute limit is removed). Yeah it failed only because the migration code retried few times and we bailed out which is wrong as well. I will send two patches as a reply to this email. > >> This is really strange! As you write in other email the page is > >> reserved. That means that some of the earlier checks > >> if (zone_idx(zone) == ZONE_MOVABLE) > >> return false; > >> mt = get_pageblock_migratetype(page); > >> if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) > > > > The MIGRATE_MOVABLE check is indeed bogus, because that doesn't > > guarantee there are no unmovable pages in the block (CMA block OTOH > > should be a guarantee). > > OK I'll try that and get back to you. Thanks! -- 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>
