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SubjectRe: [PATCH 1/2] mm: Disable zone_reclaim_mode by default

On 2014-04-07 23:34:27 +0100, Mel Gorman wrote:
> zone_reclaim_mode causes processes to prefer reclaiming memory from local
> node instead of spilling over to other nodes. This made sense initially when
> NUMA machines were almost exclusively HPC and the workload was partitioned
> into nodes. The NUMA penalties were sufficiently high to justify reclaiming
> the memory. On current machines and workloads it is often the case that
> zone_reclaim_mode destroys performance but not all users know how to detect
> this. Favour the common case and disable it by default. Users that are
> sophisticated enough to know they need zone_reclaim_mode will detect it.

Unsurprisingly I am in favor of this.

> Documentation/sysctl/vm.txt | 17 +++++++++--------
> mm/page_alloc.c | 2 --
> 2 files changed, 9 insertions(+), 10 deletions(-)

But I think linux/topology.h's comment about RECLAIM_DISTANCE should be
adapted as well.



Andres Freund
PostgreSQL Development, 24x7 Support, Training & Services

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