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-rw-r--r--mm/vmscan.c44
1 files changed, 39 insertions, 5 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index efbcab1c8f5..3b8ede88239 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2163,6 +2163,42 @@ static void shrink_zone(int priority, struct zone *zone,
} while (memcg);
}
+/* Returns true if compaction should go ahead for a high-order request */
+static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
+{
+ unsigned long balance_gap, watermark;
+ bool watermark_ok;
+
+ /* Do not consider compaction for orders reclaim is meant to satisfy */
+ if (sc->order <= PAGE_ALLOC_COSTLY_ORDER)
+ return false;
+
+ /*
+ * Compaction takes time to run and there are potentially other
+ * callers using the pages just freed. Continue reclaiming until
+ * there is a buffer of free pages available to give compaction
+ * a reasonable chance of completing and allocating the page
+ */
+ balance_gap = min(low_wmark_pages(zone),
+ (zone->present_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
+ KSWAPD_ZONE_BALANCE_GAP_RATIO);
+ watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
+ watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
+
+ /*
+ * If compaction is deferred, reclaim up to a point where
+ * compaction will have a chance of success when re-enabled
+ */
+ if (compaction_deferred(zone))
+ return watermark_ok;
+
+ /* If compaction is not ready to start, keep reclaiming */
+ if (!compaction_suitable(zone, sc->order))
+ return false;
+
+ return watermark_ok;
+}
+
/*
* This is the direct reclaim path, for page-allocating processes. We only
* try to reclaim pages from zones which will satisfy the caller's allocation
@@ -2180,8 +2216,8 @@ static void shrink_zone(int priority, struct zone *zone,
* scan then give up on it.
*
* This function returns true if a zone is being reclaimed for a costly
- * high-order allocation and compaction is either ready to begin or deferred.
- * This indicates to the caller that it should retry the allocation or fail.
+ * high-order allocation and compaction is ready to begin. This indicates to
+ * the caller that it should retry the allocation or fail.
*/
static bool shrink_zones(int priority, struct zonelist *zonelist,
struct scan_control *sc)
@@ -2215,9 +2251,7 @@ static bool shrink_zones(int priority, struct zonelist *zonelist,
* noticable problem, like transparent huge page
* allocations.
*/
- if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
- (compaction_suitable(zone, sc->order) ||
- compaction_deferred(zone))) {
+ if (compaction_ready(zone, sc)) {
should_abort_reclaim = true;
continue;
}