Messages in this thread | | | Subject | Re: [PATCH 21/27] mm, vmscan: Only wakeup kswapd once per node for the requested classzone | From | Vlastimil Babka <> | Date | Fri, 17 Jun 2016 12:46:05 +0200 |
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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@techsingularity.net> > --- > 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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