| 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. |
