Re: [PATCH 1/4] mm: vmscan: Correct check for kswapd sleeping in sleeping_prematurely
From: Minchan Kim <hidden>
Date: 2011-06-27 06:11:22
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On Fri, Jun 24, 2011 at 11:44 PM, Mel Gorman [off-list ref] 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 <redacted> Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Minchan Kim <redacted> -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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=mailto:"dont@kvack.org"> email@kvack.org </a>