The patch titled
kswapd: assign new_order and new_classzone_idx after wakeup in sleeping
has been added to the -mm tree. Its filename is
kswapd-assign-new_order-and-new_classzone_idx-after-wakeup-in-sleeping.patch
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Subject: kswapd: assign new_order and new_classzone_idx after wakeup in sleeping
From: "Alex,Shi" <alex.shi@xxxxxxxxx>
There 2 places to read pgdat in kswapd. One is return from a successful
balance, another is waked up from kswapd sleeping. The new_order and
new_classzone_idx represent the balance input order and classzone_idx.
But current new_order and new_classzone_idx are not assigned after
kswapd_try_to_sleep(), that will cause a bug in the following scenario.
1: after a successful balance, kswapd goes to sleep, and new_order = 0;
new_classzone_idx = __MAX_NR_ZONES - 1;
2: kswapd waked up with order = 3 and classzone_idx = ZONE_NORMAL
3: in the balance_pgdat() running, a new balance wakeup happened with
order = 5, and classzone_idx = ZONE_NORMAL
4: the first wakeup(order = 3) finished successufly, return order = 3
but, the new_order is still 0, so, this balancing will be treated as a
failed balance. And then the second tighter balancing will be missed.
So, to avoid the above problem, the new_order and new_classzone_idx need
to be assigned for later successful comparison.
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxx>
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Tested-by: Pádraig Brady <P@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 2 ++
1 file changed, 2 insertions(+)
diff -puN mm/vmscan.c~kswapd-assign-new_order-and-new_classzone_idx-after-wakeup-in-sleeping mm/vmscan.c
--- a/mm/vmscan.c~kswapd-assign-new_order-and-new_classzone_idx-after-wakeup-in-sleeping
+++ a/mm/vmscan.c
@@ -2883,6 +2883,8 @@ static int kswapd(void *p)
balanced_classzone_idx);
order = pgdat->kswapd_max_order;
classzone_idx = pgdat->classzone_idx;
+ new_order = order;
+ new_classzone_idx = classzone_idx;
pgdat->kswapd_max_order = 0;
pgdat->classzone_idx = pgdat->nr_zones - 1;
}
_
Patches currently in -mm which might be from alex.shi@xxxxxxxxx are
linux-next.patch
kswapd-avoid-unnecessary-rebalance-after-an-unsuccessful-balancing.patch
kswapd-assign-new_order-and-new_classzone_idx-after-wakeup-in-sleeping.patch
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