| 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. |