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 <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
