lkml.org 
[lkml]   [2022]   [Jun]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    SubjectRe: [RFC PATCH v4 7/7] mm/demotion: Demote pages according to allocation fallback order
    Date
    Ying Huang <ying.huang@intel.com> writes:

    .....

    > > > >
    >> > > > https://lore.kernel.org/lkml/69f2d063a15f8c4afb4688af7b7890f32af55391.camel@intel.com/
    >> > > >
    >> > > > 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@mail.gmail.com/
    >
    > 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);
    \
     
     \ /
      Last update: 2022-06-06 08:29    [W:6.140 / U:0.096 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site