On Thu, 11 Jul 2019 02:42:56 +0800 Mike Kravetz wrote:
>
> It is quite easy to hit the condition where:
> nr_reclaimed == 0 && nr_scanned == 0 is true, but we skip the previous test
>
Then skipping check of __GFP_RETRY_MAYFAIL makes no sense in your case.
It is restored in respin below.
> and the compaction check:
> sc->nr_reclaimed < pages_for_compaction &&
> inactive_lru_pages > pages_for_compaction
> is true, so we return true before the below check of costly_fg_reclaim
>
This check is placed after COMPACT_SUCCESS; the latter is used to
replace sc->nr_reclaimed < pages_for_compaction.
And dryrun detection is added based on the result of last round of
shrinking of inactive pages, particularly when their number is large
enough.
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2571,18 +2571,6 @@ 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];
@@ -2598,7 +2586,21 @@ 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)
--
