On 08/23/2018 02:21 PM, Michal Hocko wrote: > On Thu 23-08-18 14:10:28, Vlastimil Babka wrote: >> It also shows that all orders except order-9 are in fact plentiful. >> Michal's earlier summary of the trace shows that most allocations are up >> to order-3 and should be fine, the exception is THP: >> >> 277 9 GFP_TRANSHUGE|__GFP_THISNODE > > But please note that this is not from the time when the page cache > dropped to the observed values. So we do not know what happened at the > time. Okay, we didn't observe it drop, but there must still be something going on that keeps it from growing back? > Anyway 277 THP pages paging out such a large page cache amount would be > more than unexpected even for explicitly costly THP fault in methods. It's 277 in 90 seconds. But it seems no reclaim should happen there anyway, because shrink_zones() should evaluate compaction_ready() as true and skip the zones. Unless there is some kind of bug, maybe e.g. ZONE_DMA returns compaction_ready() as false, causing the whole node to be reclaimed? Hmm.
