On Fri, Jun 24, 2011 at 11:44 PM, Mel Gorman <mgorman@xxxxxxx> 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@xxxxxxxxxxxxxx> > Signed-off-by: Mel Gorman <mgorman@xxxxxxx> Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx> -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href