[lkml]   [2011]   [Jun]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 1/4] mm: vmscan: Correct check for kswapd sleeping in sleeping_prematurely
On Fri, Jun 24, 2011 at 11:44 PM, 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 <>
> Signed-off-by: Mel Gorman <>
Reviewed-by: Minchan Kim <>

Kind regards,
Minchan Kim
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2011-06-27 08:27    [W:0.103 / U:1.472 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site