Messages in this thread | | | Date | Thu, 30 Jun 2011 11:23:39 +0900 | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 1/4] mm: vmscan: Correct check for kswapd sleeping in sleeping_prematurely |
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(2011/06/24 23:44), Mel Gorman wrote: > During allocator-intensive workloads, kswapd will be woken frequently > causing free memory to oscillate between the high and min watermark. > This is expected behaviour. > > A problem occurs if the highest zone is small. balance_pgdat() > only considers unreclaimable zones when priority is DEF_PRIORITY > but sleeping_prematurely considers all zones. It's possible for this > sequence to occur > > 1. kswapd wakes up and enters balance_pgdat() > 2. At DEF_PRIORITY, marks highest zone unreclaimable > 3. At DEF_PRIORITY-1, ignores highest zone setting end_zone > 4. At DEF_PRIORITY-1, calls shrink_slab freeing memory from > highest zone, clearing all_unreclaimable. Highest zone > is still unbalanced > 5. kswapd returns and calls sleeping_prematurely > 6. sleeping_prematurely looks at *all* zones, not just the ones > being considered by balance_pgdat. The highest small zone > has all_unreclaimable cleared but but the zone is not > balanced. all_zones_ok is false so kswapd stays awake > > This patch corrects the behaviour of sleeping_prematurely to check > the zones balance_pgdat() checked. > > Reported-and-tested-by: Pádraig Brady <P@draigBrady.com> > Signed-off-by: Mel Gorman <mgorman@suse.de> > --- > mm/vmscan.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 8ff834e..841e3bf 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2323,7 +2323,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, > return true; > > /* Check the watermark levels */ > - for (i = 0; i < pgdat->nr_zones; i++) { > + for (i = 0; i <= classzone_idx; i++) { > struct zone *zone = pgdat->node_zones + i; > > if (!populated_zone(zone))
sorry for the delay. Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
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