By default NUMA balancing does not scan or prot_none private-node folios, so the kernel never migrates them via access sampling.
Add NODE_PRIVATE_CAP_NUMA_BALANCING to opt a private node in. Add folio_allows_numa_balance() to gate change_prot_numa() scans on node eligibility. Opted-in private node participate like normal. Unlike demotion, NUMA balancing is not reclaim-driven, so this capability stands alone and does not require CAP_RECLAIM. Signed-off-by: Gregory Price <[email protected]> --- include/linux/node_private.h | 29 +++++++++++++++++++++++++++++ mm/internal.h | 13 +++++++++++++ mm/mempolicy.c | 2 +- 3 files changed, 43 insertions(+), 1 deletion(-) diff --git a/include/linux/node_private.h b/include/linux/node_private.h index 87b03444b2c97..5c3e070ed0deb 100644 --- a/include/linux/node_private.h +++ b/include/linux/node_private.h @@ -16,6 +16,7 @@ struct page; #define NODE_PRIVATE_CAP_USER_NUMA (1UL << 1) /* allow mempolicy */ #define NODE_PRIVATE_CAP_HOTUNPLUG (1UL << 2) /* allow hot-unplug */ #define NODE_PRIVATE_CAP_DEMOTION (1UL << 3) /* allow tiering demotion */ +#define NODE_PRIVATE_CAP_NUMA_BALANCING (1UL << 4) /* allow NUMA balancing */ /** * struct node_private - Per-node container for N_MEMORY_PRIVATE nodes @@ -143,6 +144,29 @@ static inline bool node_allows_demotion(int nid) return ret; } +/** + * node_allows_numa_balancing - may NUMA balancing scan/migrate this node? + * @nid: the node to test + * + * Access-based promotion/migration. Unlike demotion this is not reclaim-driven, + * so CAP_NUMA_BALANCING stands alone (no CAP_RECLAIM dependency). + * + * return: true for normal nodes and private nodes opted into CAP_NUMA_BALANCING. + */ +static inline bool node_allows_numa_balancing(int nid) +{ + struct node_private *np; + bool ret; + + if (!node_state(nid, N_MEMORY_PRIVATE)) + return true; + rcu_read_lock(); + np = rcu_dereference(NODE_DATA(nid)->node_private); + ret = np && (np->caps & NODE_PRIVATE_CAP_NUMA_BALANCING); + rcu_read_unlock(); + return ret; +} + #else /* !CONFIG_NUMA */ static inline bool folio_is_private_node(struct folio *folio) @@ -180,6 +204,11 @@ static inline bool node_allows_demotion(int nid) return true; } +static inline bool node_allows_numa_balancing(int nid) +{ + return true; +} + #endif /* CONFIG_NUMA */ #if defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG) diff --git a/mm/internal.h b/mm/internal.h index 62e68acae08a3..01ab8b32b0bd8 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -123,6 +123,19 @@ static inline bool folio_allows_madvise(struct folio *folio) node_allows_reclaim(folio_nid(folio)); } +/* + * folio_allows_numa_balance() - may NUMA balancing scan/migrate this folio? + * + * NUMA balancing is access-aware tiering migration, so it follows the tiering + * opt-in: false for ZONE_DEVICE and for N_MEMORY_PRIVATE nodes without + * CAP_NUMA_BALANCING, true for all other folios. + */ +static inline bool folio_allows_numa_balance(struct folio *folio) +{ + return !folio_is_zone_device(folio) && + node_allows_numa_balancing(folio_nid(folio)); +} + /* * folio_allows_longterm_pin() - may this folio be long-term GUP-pinned? * diff --git a/mm/mempolicy.c b/mm/mempolicy.c index fe42a510590a2..4daba81fff7c7 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -874,7 +874,7 @@ bool folio_can_map_prot_numa(struct folio *folio, struct vm_area_struct *vma, { int nid; - if (!folio || folio_is_private_managed(folio) || folio_test_ksm(folio)) + if (!folio || !folio_allows_numa_balance(folio) || folio_test_ksm(folio)) return false; /* Also skip shared copy-on-write folios */ -- 2.53.0-Meta
