On 7/31/19 4:08 AM, Vlastimil Babka wrote: > > I agree this is an improvement overall, but perhaps the patch does too > many things at once. The reshuffle is one thing and makes sense. The > change of the last return condition could perhaps be separate. Also > AFAICS the ultimate result is that when nr_reclaimed == 0, the function > will now always return false. Which makes the initial test for > __GFP_RETRY_MAYFAIL and the comments there misleading. There will no > longer be a full LRU scan guaranteed - as long as the scanned LRU chunk > yields no reclaimed page, we abort.
Can someone help me understand why nr_scanned == 0 guarantees a full LRU scan? FWICS, nr_scanned used in this context is only incremented in shrink_page_list and potentially shrink_zones. In the stall case I am looking at, there are MANY cases in which nr_scanned is only a few pages and none of those are reclaimed. Can we not get nr_scanned == 0 on an arbitrary chunk of the LRU? I must be missing something, because I do not see how nr_scanned == 0 guarantees a full scan. -- Mike Kravetz
