On Mon, 2022-06-06 at 11:51 +0530, Aneesh Kumar K.V wrote: > 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); Firstly, it addressed my requirement, Thanks! And, I'd prefer to put mtc definition in alloc_demote_page(). Because that makes all page allocation logic in one function. Thus the readability of code is better. Best Regards, Huang, Ying > if (current_is_kswapd()) > __count_vm_events(PGDEMOTE_KSWAPD, nr_succeeded);
