From: Hillf Danton <[email protected]> Address the issue of should_continue_reclaim returning true too often for __GFP_RETRY_MAYFAIL attempts when !nr_reclaimed and nr_scanned. This was observed during hugetlb page allocation causing stalls for minutes or hours.
We can stop reclaiming pages if compaction reports it can make a progress. There might be side-effects for other high-order allocations that would potentially benefit from reclaiming more before compaction so that they would be faster and less likely to stall. However, the consequences of premature/over-reclaim are considered worse. We can also bail out of reclaiming pages if we know that there are not enough inactive lru pages left to satisfy the costly allocation. We can give up reclaiming pages too if we see dryrun occur, with the certainty of plenty of inactive pages. IOW with dryrun detected, we are sure we have reclaimed as many pages as we could. Cc: Mike Kravetz <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Johannes Weiner <[email protected]> Signed-off-by: Hillf Danton <[email protected]> Tested-by: Mike Kravetz <[email protected]> Acked-by: Mel Gorman <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Signed-off-by: Mike Kravetz <[email protected]> --- v2 - Updated commit message and added SOB. mm/vmscan.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 47aa2158cfac..a386c5351592 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2738,18 +2738,6 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat, return false; } - /* - * If we have not reclaimed enough pages for compaction and the - * inactive lists are large enough, continue reclaiming - */ - pages_for_compaction = compact_gap(sc->order); - inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE); - if (get_nr_swap_pages() > 0) - inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON); - if (sc->nr_reclaimed < pages_for_compaction && - inactive_lru_pages > pages_for_compaction) - return true; - /* If compaction would go ahead or the allocation would succeed, stop */ for (z = 0; z <= sc->reclaim_idx; z++) { struct zone *zone = &pgdat->node_zones[z]; @@ -2765,7 +2753,21 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat, ; } } - return true; + + /* + * If we have not reclaimed enough pages for compaction and the + * inactive lists are large enough, continue reclaiming + */ + pages_for_compaction = compact_gap(sc->order); + inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE); + if (get_nr_swap_pages() > 0) + inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON); + + return inactive_lru_pages > pages_for_compaction && + /* + * avoid dryrun with plenty of inactive pages + */ + nr_scanned && nr_reclaimed; } static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg) -- 2.20.1
