mm: Convert workingset to XArray
We construct an XA_STATE and use it to delete the node with xas_store() rather than adding a special function for this unique use case. Includes a test that simulates this usage for the test suite. Signed-off-by: Matthew Wilcox <willy@infradead.org>
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@ -306,15 +306,6 @@ void workingset_update_node(struct xa_node *node);
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xas_set_update(xas, workingset_update_node); \
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} while (0)
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/* Returns workingset_update_node() if the mapping has shadow entries. */
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#define workingset_lookup_update(mapping) \
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({ \
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radix_tree_update_node_t __helper = workingset_update_node; \
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if (dax_mapping(mapping) || shmem_mapping(mapping)) \
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__helper = NULL; \
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__helper; \
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})
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/* linux/mm/page_alloc.c */
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extern unsigned long totalram_pages;
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extern unsigned long totalreserve_pages;
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@ -863,6 +863,67 @@ static noinline void check_create_range(struct xarray *xa)
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check_create_range_3();
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}
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static LIST_HEAD(shadow_nodes);
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static void test_update_node(struct xa_node *node)
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{
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if (node->count && node->count == node->nr_values) {
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if (list_empty(&node->private_list))
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list_add(&shadow_nodes, &node->private_list);
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} else {
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if (!list_empty(&node->private_list))
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list_del_init(&node->private_list);
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}
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}
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static noinline void shadow_remove(struct xarray *xa)
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{
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struct xa_node *node;
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xa_lock(xa);
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while ((node = list_first_entry_or_null(&shadow_nodes,
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struct xa_node, private_list))) {
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XA_STATE(xas, node->array, 0);
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XA_BUG_ON(xa, node->array != xa);
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list_del_init(&node->private_list);
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xas.xa_node = xa_parent_locked(node->array, node);
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xas.xa_offset = node->offset;
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xas.xa_shift = node->shift + XA_CHUNK_SHIFT;
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xas_set_update(&xas, test_update_node);
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xas_store(&xas, NULL);
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}
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xa_unlock(xa);
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}
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static noinline void check_workingset(struct xarray *xa, unsigned long index)
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{
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XA_STATE(xas, xa, index);
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xas_set_update(&xas, test_update_node);
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do {
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xas_lock(&xas);
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xas_store(&xas, xa_mk_value(0));
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xas_next(&xas);
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xas_store(&xas, xa_mk_value(1));
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xas_unlock(&xas);
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} while (xas_nomem(&xas, GFP_KERNEL));
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XA_BUG_ON(xa, list_empty(&shadow_nodes));
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xas_lock(&xas);
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xas_next(&xas);
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xas_store(&xas, &xas);
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XA_BUG_ON(xa, !list_empty(&shadow_nodes));
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xas_store(&xas, xa_mk_value(2));
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xas_unlock(&xas);
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XA_BUG_ON(xa, list_empty(&shadow_nodes));
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shadow_remove(xa);
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XA_BUG_ON(xa, !list_empty(&shadow_nodes));
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XA_BUG_ON(xa, !xa_empty(xa));
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}
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static noinline void check_destroy(struct xarray *xa)
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{
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unsigned long index;
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@ -916,6 +977,10 @@ static int xarray_checks(void)
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check_create_range(&array);
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check_store_iter(&array);
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check_workingset(&array, 0);
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check_workingset(&array, 64);
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check_workingset(&array, 4096);
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printk("XArray: %u of %u tests passed\n", tests_passed, tests_run);
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return (tests_run == tests_passed) ? 0 : -EINVAL;
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}
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@ -148,7 +148,7 @@
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* and activations is maintained (node->inactive_age).
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*
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* On eviction, a snapshot of this counter (along with some bits to
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* identify the node) is stored in the now empty page cache radix tree
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* identify the node) is stored in the now empty page cache
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* slot of the evicted page. This is called a shadow entry.
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*
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* On cache misses for which there are shadow entries, an eligible
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@ -162,7 +162,7 @@
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/*
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* Eviction timestamps need to be able to cover the full range of
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* actionable refaults. However, bits are tight in the radix tree
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* actionable refaults. However, bits are tight in the xarray
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* entry, and after storing the identifier for the lruvec there might
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* not be enough left to represent every single actionable refault. In
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* that case, we have to sacrifice granularity for distance, and group
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@ -339,7 +339,7 @@ out:
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static struct list_lru shadow_nodes;
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void workingset_update_node(struct radix_tree_node *node)
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void workingset_update_node(struct xa_node *node)
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{
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/*
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* Track non-empty nodes that contain only shadow entries;
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@ -368,7 +368,7 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
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nodes = list_lru_shrink_count(&shadow_nodes, sc);
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/*
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* Approximate a reasonable limit for the radix tree nodes
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* Approximate a reasonable limit for the nodes
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* containing shadow entries. We don't need to keep more
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* shadow entries than possible pages on the active list,
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* since refault distances bigger than that are dismissed.
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@ -383,11 +383,11 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
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* worst-case density of 1/8th. Below that, not all eligible
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* refaults can be detected anymore.
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*
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* On 64-bit with 7 radix_tree_nodes per page and 64 slots
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* On 64-bit with 7 xa_nodes per page and 64 slots
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* each, this will reclaim shadow entries when they consume
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* ~1.8% of available memory:
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*
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* PAGE_SIZE / radix_tree_nodes / node_entries * 8 / PAGE_SIZE
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* PAGE_SIZE / xa_nodes / node_entries * 8 / PAGE_SIZE
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*/
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if (sc->memcg) {
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cache = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
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@ -396,7 +396,7 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
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cache = node_page_state(NODE_DATA(sc->nid), NR_ACTIVE_FILE) +
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node_page_state(NODE_DATA(sc->nid), NR_INACTIVE_FILE);
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}
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max_nodes = cache >> (RADIX_TREE_MAP_SHIFT - 3);
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max_nodes = cache >> (XA_CHUNK_SHIFT - 3);
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if (!nodes)
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return SHRINK_EMPTY;
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@ -409,11 +409,11 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
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static enum lru_status shadow_lru_isolate(struct list_head *item,
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struct list_lru_one *lru,
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spinlock_t *lru_lock,
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void *arg)
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void *arg) __must_hold(lru_lock)
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{
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struct xa_node *node = container_of(item, struct xa_node, private_list);
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XA_STATE(xas, node->array, 0);
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struct address_space *mapping;
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struct radix_tree_node *node;
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unsigned int i;
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int ret;
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/*
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@ -421,14 +421,13 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
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* the shadow node LRU under the i_pages lock and the
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* lru_lock. Because the page cache tree is emptied before
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* the inode can be destroyed, holding the lru_lock pins any
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* address_space that has radix tree nodes on the LRU.
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* address_space that has nodes on the LRU.
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*
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* We can then safely transition to the i_pages lock to
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* pin only the address_space of the particular node we want
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* to reclaim, take the node off-LRU, and drop the lru_lock.
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*/
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node = container_of(item, struct xa_node, private_list);
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mapping = container_of(node->array, struct address_space, i_pages);
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/* Coming from the list, invert the lock order */
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@ -450,25 +449,17 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
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goto out_invalid;
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if (WARN_ON_ONCE(node->count != node->nr_values))
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goto out_invalid;
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for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
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if (node->slots[i]) {
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if (WARN_ON_ONCE(!xa_is_value(node->slots[i])))
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goto out_invalid;
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if (WARN_ON_ONCE(!node->nr_values))
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goto out_invalid;
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if (WARN_ON_ONCE(!mapping->nrexceptional))
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goto out_invalid;
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node->slots[i] = NULL;
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node->nr_values--;
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node->count--;
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mapping->nrexceptional--;
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}
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}
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if (WARN_ON_ONCE(node->nr_values))
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goto out_invalid;
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mapping->nrexceptional -= node->nr_values;
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xas.xa_node = xa_parent_locked(&mapping->i_pages, node);
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xas.xa_offset = node->offset;
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xas.xa_shift = node->shift + XA_CHUNK_SHIFT;
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xas_set_update(&xas, workingset_update_node);
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/*
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* We could store a shadow entry here which was the minimum of the
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* shadow entries we were tracking ...
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*/
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xas_store(&xas, NULL);
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inc_lruvec_page_state(virt_to_page(node), WORKINGSET_NODERECLAIM);
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__radix_tree_delete_node(&mapping->i_pages, node,
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workingset_lookup_update(mapping));
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out_invalid:
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xa_unlock_irq(&mapping->i_pages);
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