Ying Huang <ying.huang@xxxxxxxxx> writes: ..... > > > > >> > > > https://lore.kernel.org/lkml/69f2d063a15f8c4afb4688af7b7890f32af55391.camel@xxxxxxxxx/ >> > > > >> > > > That is, something like below, >> > > > >> > > > static struct page *alloc_demote_page(struct page *page, unsigned long node) >> > > > { >> > > > struct page *page; >> > > > nodemask_t allowed_mask; >> > > > struct migration_target_control mtc = { >> > > > /* >> > > > * Allocate from 'node', or fail quickly and quietly. >> > > > * When this happens, 'page' will likely just be discarded >> > > > * instead of migrated. >> > > > */ >> > > > .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | >> > > > __GFP_THISNODE | __GFP_NOWARN | >> > > > __GFP_NOMEMALLOC | GFP_NOWAIT, >> > > > .nid = node >> > > > }; >> > > > >> > > > page = alloc_migration_target(page, (unsigned long)&mtc); >> > > > if (page) >> > > > return page; >> > > > >> > > > mtc.gfp_mask &= ~__GFP_THISNODE; >> > > > mtc.nmask = &allowed_mask; >> > > > >> > > > return alloc_migration_target(page, (unsigned long)&mtc); >> > > > } >> > > >> > > I skipped doing this in v5 because I was not sure this is really what we >> > > want. >> > >> > I think so. And this is the original behavior. We should keep the >> > original behavior as much as possible, then make changes if necessary. >> > >> >> That is the reason I split the new page allocation as a separate patch. >> Previous discussion on this topic didn't conclude on whether we really >> need to do the above or not >> https://lore.kernel.org/lkml/CAAPL-u9endrWf_aOnPENDPdvT-2-YhCAeJ7ONGckGnXErTLOfQ@xxxxxxxxxxxxxx/ > > Please check the later email in the thread you referenced. Both Wei and > me agree that the use case needs to be supported. We just didn't reach > concensus about how to implement it. If you think Wei's solution is > better (referenced as below), you can try to do that too. Although I > think my proposed implementation is much simpler. How about the below details diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h index 79bd8d26feb2..cd6e71f702ad 100644 --- a/include/linux/memory-tiers.h +++ b/include/linux/memory-tiers.h @@ -21,6 +21,7 @@ void node_remove_from_memory_tier(int node); int node_get_memory_tier_id(int node); int node_set_memory_tier(int node, int tier); int node_reset_memory_tier(int node, int tier); +void node_get_allowed_targets(int node, nodemask_t *targets); #else #define numa_demotion_enabled false static inline int next_demotion_node(int node) @@ -28,6 +29,10 @@ static inline int next_demotion_node(int node) return NUMA_NO_NODE; } +static inline void node_get_allowed_targets(int node, nodemask_t *targets) +{ + *targets = NODE_MASK_NONE; +} #endif /* CONFIG_TIERED_MEMORY */ #endif diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c index b4e72b672d4d..592d939ec28d 100644 --- a/mm/memory-tiers.c +++ b/mm/memory-tiers.c @@ -18,6 +18,7 @@ struct memory_tier { struct demotion_nodes { nodemask_t preferred; + nodemask_t allowed; }; #define to_memory_tier(device) container_of(device, struct memory_tier, dev) @@ -378,6 +379,25 @@ int node_set_memory_tier(int node, int tier) } EXPORT_SYMBOL_GPL(node_set_memory_tier); +void node_get_allowed_targets(int node, nodemask_t *targets) +{ + /* + * node_demotion[] is updated without excluding this + * function from running. + * + * If any node is moving to lower tiers then modifications + * in node_demotion[] are still valid for this node, if any + * node is moving to higher tier then moving node may be + * used once for demotion which should be ok so rcu should + * be enough here. + */ + rcu_read_lock(); + + *targets = node_demotion[node].allowed; + + rcu_read_unlock(); +} + /** * next_demotion_node() - Get the next node in the demotion path * @node: The starting node to lookup the next node @@ -437,8 +457,10 @@ static void __disable_all_migrate_targets(void) { int node; - for_each_node_mask(node, node_states[N_MEMORY]) + for_each_node_mask(node, node_states[N_MEMORY]) { node_demotion[node].preferred = NODE_MASK_NONE; + node_demotion[node].allowed = NODE_MASK_NONE; + } } static void disable_all_migrate_targets(void) @@ -465,7 +487,7 @@ static void establish_migration_targets(void) struct demotion_nodes *nd; int target = NUMA_NO_NODE, node; int distance, best_distance; - nodemask_t used; + nodemask_t used, allowed = NODE_MASK_NONE; if (!node_demotion) return; @@ -511,6 +533,29 @@ static void establish_migration_targets(void) } } while (1); } + /* + * Now build the allowed mask for each node collecting node mask from + * all memory tier below it. This allows us to fallback demotion page + * allocation to a set of nodes that is closer the above selected + * perferred node. + */ + list_for_each_entry(memtier, &memory_tiers, list) + nodes_or(allowed, allowed, memtier->nodelist); + /* + * Removes nodes not yet in N_MEMORY. + */ + nodes_and(allowed, node_states[N_MEMORY], allowed); + + list_for_each_entry(memtier, &memory_tiers, list) { + /* + * Keep removing current tier from allowed nodes, + * This will remove all nodes in current and above + * memory tier from the allowed mask. + */ + nodes_andnot(allowed, allowed, memtier->nodelist); + for_each_node_mask(node, memtier->nodelist) + node_demotion[node].allowed = allowed; + } } /* diff --git a/mm/vmscan.c b/mm/vmscan.c index 3a8f78277f99..b0792d838efb 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1460,19 +1460,32 @@ static void folio_check_dirty_writeback(struct folio *folio, mapping->a_ops->is_dirty_writeback(folio, dirty, writeback); } -static struct page *alloc_demote_page(struct page *page, unsigned long node) +static struct page *alloc_demote_page(struct page *page, unsigned long private) { - struct migration_target_control mtc = { - /* - * Allocate from 'node', or fail quickly and quietly. - * When this happens, 'page' will likely just be discarded - * instead of migrated. - */ - .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | - __GFP_THISNODE | __GFP_NOWARN | - __GFP_NOMEMALLOC | GFP_NOWAIT, - .nid = node - }; + struct page *target_page; + nodemask_t *allowed_mask; + struct migration_target_control *mtc; + + mtc = (struct migration_target_control *)private; + + allowed_mask = mtc->nmask; + /* + * make sure we allocate from the target node first also trying to + * reclaim pages from the target node via kswapd if we are low on + * free memory on target node. If we don't do this and if we have low + * free memory on the target memtier, we would start allocating pages + * from higher memory tiers without even forcing a demotion of cold + * pages from the target memtier. This can result in the kernel placing + * hotpages in higher memory tiers. + */ + mtc->nmask = NULL; + mtc->gfp_mask |= __GFP_THISNODE; + target_page = alloc_migration_target(page, (unsigned long)&mtc); + if (target_page) + return target_page; + + mtc->gfp_mask &= ~__GFP_THISNODE; + mtc->nmask = allowed_mask; return alloc_migration_target(page, (unsigned long)&mtc); } @@ -1487,6 +1500,19 @@ static unsigned int demote_page_list(struct list_head *demote_pages, { int target_nid = next_demotion_node(pgdat->node_id); unsigned int nr_succeeded; + nodemask_t allowed_mask; + + struct migration_target_control mtc = { + /* + * Allocate from 'node', or fail quickly and quietly. + * When this happens, 'page' will likely just be discarded + * instead of migrated. + */ + .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN | + __GFP_NOMEMALLOC | GFP_NOWAIT, + .nid = target_nid, + .nmask = &allowed_mask + }; if (list_empty(demote_pages)) return 0; @@ -1494,10 +1520,12 @@ static unsigned int demote_page_list(struct list_head *demote_pages, if (target_nid == NUMA_NO_NODE) return 0; + node_get_allowed_targets(pgdat->node_id, &allowed_mask); + /* Demotion ignores all cpuset and mempolicy settings */ migrate_pages(demote_pages, alloc_demote_page, NULL, - target_nid, MIGRATE_ASYNC, MR_DEMOTION, - &nr_succeeded); + (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION, + &nr_succeeded); if (current_is_kswapd()) __count_vm_events(PGDEMOTE_KSWAPD, nr_succeeded);
