Page reclaim at priority 0 will scan the entire LRU as priority 0 is
considered to be a near OOM condition. Direct reclaim can reach this
priority while still making reclaim progress. This patch avoids
reclaiming at priority 0 unless no reclaim progress was made and
the page allocator would consider firing the OOM killer. The
user-visible impact is that direct reclaim will not easily reach
priority 0 and start swapping prematurely.
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
---
mm/vmscan.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index fe73724..65f2fbea 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2382,12 +2382,14 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
struct zone *zone;
unsigned long writeback_threshold;
bool aborted_reclaim;
+ int min_scan_priority = 1;
delayacct_freepages_start();
if (global_reclaim(sc))
count_vm_event(ALLOCSTALL);
+rescan:
do {
vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
sc->priority);
@@ -2442,7 +2444,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
WB_REASON_TRY_TO_FREE_PAGES);
sc->may_writepage = 1;
}
- } while (--sc->priority >= 0);
+ } while (--sc->priority >= min_scan_priority);
out:
delayacct_freepages_end();
@@ -2466,6 +2468,12 @@ out:
if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
return 1;
+ /* If the page allocator is considering OOM, rescan at priority 0 */
+ if (min_scan_priority) {
+ min_scan_priority = 0;
+ goto rescan;
+ }
+
return 0;
}
--
1.8.1.4
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