Messages in this thread | | | Date | Mon, 28 Jul 2014 10:42:05 +0200 | From | Vlastimil Babka <> | Subject | Re: [patch v3] mm, thp: only collapse hugepages to nodes with affinity for zone_reclaim_mode |
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On 07/17/2014 02:59 AM, David Rientjes wrote: > Commit 9f1b868a13ac ("mm: thp: khugepaged: add policy for finding target > node") improved the previous khugepaged logic which allocated a > transparent hugepages from the node of the first page being collapsed. > > However, it is still possible to collapse pages to remote memory which may > suffer from additional access latency. With the current policy, it is > possible that 255 pages (with PAGE_SHIFT == 12) will be collapsed remotely > if the majority are allocated from that node. > > When zone_reclaim_mode is enabled, it means the VM should make every attempt > to allocate locally to prevent NUMA performance degradation. In this case, > we do not want to collapse hugepages to remote nodes that would suffer from > increased access latency. Thus, when zone_reclaim_mode is enabled, only > allow collapsing to nodes with RECLAIM_DISTANCE or less. > > There is no functional change for systems that disable zone_reclaim_mode. > > Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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