Messages in this thread Patch in this message | | | Date | Tue, 30 Aug 2016 16:00:51 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 07/34] mm, vmscan: make kswapd reclaim in terms of nodes |
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On Tue, Aug 30, 2016 at 07:55:08PM +0530, Srikar Dronamraju wrote: > > > > > > This patch seems to hurt FA_DUMP functionality. This behaviour is not > > > seen on v4.7 but only after this patch. > > > > > > So when a kernel on a multinode machine with memblock_reserve() such > > > that most of the nodes have zero available memory, kswapd seems to be > > > consuming 100% of the time. > > > > > > > Why is FA_DUMP specifically the trigger? If the nodes have zero available > > memory then is the zone_populated() check failing when FA_DUMP is enabled? If > > so, that would both allow kswapd to wake and stay awake. > > > > The trigger is memblock_reserve() for the complete node memory. And > this is exactly what FA_DUMP does. Here again the node has memory but > its all reserved so there is no free memory in the node. > > Did you mean populated_zone() when you said zone_populated or have I > mistaken? populated_zone() does return 1 since it checks for > zone->present_pages. >
Yes, I meant populated_zone(). Using present pages may have hidden a long-lived corner case as it was unexpected that an entire node would be reserved. The old code happened to survive *probably* because pgdat_reclaimable would look false and kswapd checks for pgdat being balanced would happen to do the right thing in this case.
Can you check if something like this works?
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index d572b78b65e1..cf64a5456cf6 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -830,7 +830,7 @@ unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long); static inline int populated_zone(struct zone *zone) { - return (!!zone->present_pages); + return (!!zone->managed_pages); } extern int movable_zone; -- Mel Gorman SUSE Labs
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