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What: /sys/kernel/mm/numa/
Date: June 2021
Contact: Linux memory management mailing list <linux-mm@kvack.org>
Description: Interface for NUMA
What: /sys/kernel/mm/numa/demotion_enabled
Date: June 2021
Contact: Linux memory management mailing list <linux-mm@kvack.org>
Description: Enable/disable demoting pages during reclaim
Page migration during reclaim is intended for systems
with tiered memory configurations. These systems have
multiple types of memory with varied performance
characteristics instead of plain NUMA systems where
the same kind of memory is found at varied distances.
Allowing page migration during reclaim enables these
systems to migrate pages from fast tiers to slow tiers
when the fast tier is under pressure. This migration
is performed before swap if an eligible numa node is
present in cpuset.mems for the cgroup (or if cpuset v1
is being used). If cpusets.mems changes at runtime, it
may move data to a NUMA node that does not fall into the
cpuset of the new cpusets.mems, which might be construed
to violate the guarantees of cpusets. Shared memory,
such as libraries, owned by another cgroup may still be
demoted and result in memory use on a node not present
in cpusets.mem. This should not be enabled on systems
which need strict cpuset location guarantees.
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