On 06/09/2016 08:04 PM, Mel Gorman wrote:
kswapd is woken when zones are below the low watermark but the wakeup
decision is not taking the classzone into account. Now that reclaim is
node-based, it is only required to wake kswapd once per node and only if
all zones are unbalanced for the requested classzone.
Note that one node might be checked multiple times but there is no cheap
way of tracking what nodes have already been visited for zoneslists that
be ordered by either zone or node.
Wouldn't it be possible to optimize for node order as you did in direct reclaim?
Do the zone_balanced checks when going through zonelist, and once node changes
in iteration, wake up if no eligible zones visited so far were balanced.
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7a2d69612231..b9cff9047ac0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3389,6 +3389,7 @@ static int kswapd(void *p)
void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
{
pg_data_t *pgdat;
+ int z;
if (!populated_zone(zone))
return;
@@ -3402,8 +3403,16 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
pgdat->kswapd_order = max(pgdat->kswapd_order, order);
if (!waitqueue_active(&pgdat->kswapd_wait))
return;
- if (zone_balanced(zone, order, 0))
- return;
+
+ /* Only wake kswapd if all zones are unbalanced */
+ for (z = 0; z <= classzone_idx; z++) {
+ zone = pgdat->node_zones + z;
+ if (!populated_zone(zone))
+ continue;
+
+ if (zone_balanced(zone, order, classzone_idx))
+ return;
+ }
trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
wake_up_interruptible(&pgdat->kswapd_wait);
--
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