When a high-order allocation fails, kswapd is kicked so that it reclaims
at a higher-order to avoid direct reclaimers stall and to help GFP_ATOMIC
allocations. Something has changed in recent kernels that affect the timing
where high-order GFP_ATOMIC allocations are now failing with more frequency,
particularly under pressure.
This patch pre-emptively checks if watermarks have been hit after a
high-order allocation completes successfully. If the watermarks have been
reached, kswapd is woken in the hope it fixes the watermarks before the
next GFP_ATOMIC allocation fails.
Warning, this patch is somewhat of a band-aid. If this makes a difference,
it still implies that something has changed that is either causing more
GFP_ATOMIC allocations to occur (such as the case with iwlagn wireless
driver) or make them more likely to fail.
Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
---
mm/page_alloc.c | 33 ++++++++++++++++++++++-----------
1 files changed, 22 insertions(+), 11 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7f2aa3e..851df40 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1596,6 +1596,17 @@ try_next_zone:
return page;
}
+static inline
+void wake_all_kswapd(unsigned int order, struct zonelist *zonelist,
+ enum zone_type high_zoneidx)
+{
+ struct zoneref *z;
+ struct zone *zone;
+
+ for_each_zone_zonelist(zone, z, zonelist, high_zoneidx)
+ wakeup_kswapd(zone, order);
+}
+
static inline int
should_alloc_retry(gfp_t gfp_mask, unsigned int order,
unsigned long pages_reclaimed)
@@ -1730,18 +1741,18 @@ __alloc_pages_high_priority(gfp_t gfp_mask, unsigned int order,
congestion_wait(BLK_RW_ASYNC, HZ/50);
} while (!page && (gfp_mask & __GFP_NOFAIL));
- return page;
-}
-
-static inline
-void wake_all_kswapd(unsigned int order, struct zonelist *zonelist,
- enum zone_type high_zoneidx)
-{
- struct zoneref *z;
- struct zone *zone;
+ /*
+ * If after a high-order allocation we are now below watermarks,
+ * pre-emptively kick kswapd rather than having the next allocation
+ * fail and have to wake up kswapd, potentially failing GFP_ATOMIC
+ * allocations or entering direct reclaim
+ */
+ if (unlikely(order) && page && !zone_watermark_ok(preferred_zone, order,
+ preferred_zone->watermark[ALLOC_WMARK_LOW],
+ zone_idx(preferred_zone), ALLOC_WMARK_LOW))
+ wake_all_kswapd(order, zonelist, high_zoneidx);
- for_each_zone_zonelist(zone, z, zonelist, high_zoneidx)
- wakeup_kswapd(zone, order);
+ return page;
}
static inline int
--
1.6.3.3
--
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