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mm: Convert workingset to XArray

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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>
This commit is contained in:
Matthew Wilcox 2017-11-24 14:24:59 -05:00
parent ff9c745b81
commit a97e7904c0
3 changed files with 86 additions and 39 deletions
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9
include/linux/swap.h
View File

@ -306,15 +306,6 @@ void workingset_update_node(struct xa_node *node);
xas_set_update(xas, workingset_update_node); \
} while (0)
/* Returns workingset_update_node() if the mapping has shadow entries. */
#define workingset_lookup_update(mapping) \
({ \
radix_tree_update_node_t __helper = workingset_update_node; \
if (dax_mapping(mapping) || shmem_mapping(mapping)) \
__helper = NULL; \
__helper; \
})
/* linux/mm/page_alloc.c */
extern unsigned long totalram_pages;
extern unsigned long totalreserve_pages;

65
lib/test_xarray.c
View File

@ -863,6 +863,67 @@ static noinline void check_create_range(struct xarray *xa)
check_create_range_3();
}
static LIST_HEAD(shadow_nodes);
static void test_update_node(struct xa_node *node)
{
if (node->count && node->count == node->nr_values) {
if (list_empty(&node->private_list))
list_add(&shadow_nodes, &node->private_list);
} else {
if (!list_empty(&node->private_list))
list_del_init(&node->private_list);
}
}
static noinline void shadow_remove(struct xarray *xa)
{
struct xa_node *node;
xa_lock(xa);
while ((node = list_first_entry_or_null(&shadow_nodes,
struct xa_node, private_list))) {
XA_STATE(xas, node->array, 0);
XA_BUG_ON(xa, node->array != xa);
list_del_init(&node->private_list);
xas.xa_node = xa_parent_locked(node->array, node);
xas.xa_offset = node->offset;
xas.xa_shift = node->shift + XA_CHUNK_SHIFT;
xas_set_update(&xas, test_update_node);
xas_store(&xas, NULL);
}
xa_unlock(xa);
}
static noinline void check_workingset(struct xarray *xa, unsigned long index)
{
XA_STATE(xas, xa, index);
xas_set_update(&xas, test_update_node);
do {
xas_lock(&xas);
xas_store(&xas, xa_mk_value(0));
xas_next(&xas);
xas_store(&xas, xa_mk_value(1));
xas_unlock(&xas);
} while (xas_nomem(&xas, GFP_KERNEL));
XA_BUG_ON(xa, list_empty(&shadow_nodes));
xas_lock(&xas);
xas_next(&xas);
xas_store(&xas, &xas);
XA_BUG_ON(xa, !list_empty(&shadow_nodes));
xas_store(&xas, xa_mk_value(2));
xas_unlock(&xas);
XA_BUG_ON(xa, list_empty(&shadow_nodes));
shadow_remove(xa);
XA_BUG_ON(xa, !list_empty(&shadow_nodes));
XA_BUG_ON(xa, !xa_empty(xa));
}
static noinline void check_destroy(struct xarray *xa)
{
unsigned long index;
@ -916,6 +977,10 @@ static int xarray_checks(void)
check_create_range(&array);
check_store_iter(&array);
check_workingset(&array, 0);
check_workingset(&array, 64);
check_workingset(&array, 4096);
printk("XArray: %u of %u tests passed\n", tests_passed, tests_run);
return (tests_run == tests_passed) ? 0 : -EINVAL;
}

51
mm/workingset.c
View File

@ -148,7 +148,7 @@
* and activations is maintained (node->inactive_age).
*
* On eviction, a snapshot of this counter (along with some bits to
* identify the node) is stored in the now empty page cache radix tree
* identify the node) is stored in the now empty page cache
* slot of the evicted page. This is called a shadow entry.
*
* On cache misses for which there are shadow entries, an eligible
@ -162,7 +162,7 @@
/*
* Eviction timestamps need to be able to cover the full range of
* actionable refaults. However, bits are tight in the radix tree
* actionable refaults. However, bits are tight in the xarray
* entry, and after storing the identifier for the lruvec there might
* not be enough left to represent every single actionable refault. In
* that case, we have to sacrifice granularity for distance, and group
@ -339,7 +339,7 @@ out:
static struct list_lru shadow_nodes;
void workingset_update_node(struct radix_tree_node *node)
void workingset_update_node(struct xa_node *node)
{
/*
* Track non-empty nodes that contain only shadow entries;
@ -368,7 +368,7 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
nodes = list_lru_shrink_count(&shadow_nodes, sc);
/*
* Approximate a reasonable limit for the radix tree nodes
* Approximate a reasonable limit for the nodes
* containing shadow entries. We don't need to keep more
* shadow entries than possible pages on the active list,
* since refault distances bigger than that are dismissed.
@ -383,11 +383,11 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
* worst-case density of 1/8th. Below that, not all eligible
* refaults can be detected anymore.
*
* On 64-bit with 7 radix_tree_nodes per page and 64 slots
* On 64-bit with 7 xa_nodes per page and 64 slots
* each, this will reclaim shadow entries when they consume
* ~1.8% of available memory:
*
* PAGE_SIZE / radix_tree_nodes / node_entries * 8 / PAGE_SIZE
* PAGE_SIZE / xa_nodes / node_entries * 8 / PAGE_SIZE
*/
if (sc->memcg) {
cache = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
@ -396,7 +396,7 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
cache = node_page_state(NODE_DATA(sc->nid), NR_ACTIVE_FILE) +
node_page_state(NODE_DATA(sc->nid), NR_INACTIVE_FILE);
}
max_nodes = cache >> (RADIX_TREE_MAP_SHIFT - 3);
max_nodes = cache >> (XA_CHUNK_SHIFT - 3);
if (!nodes)
return SHRINK_EMPTY;
@ -409,11 +409,11 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
static enum lru_status shadow_lru_isolate(struct list_head *item,
struct list_lru_one *lru,
spinlock_t *lru_lock,
void *arg)
void *arg) __must_hold(lru_lock)
{
struct xa_node *node = container_of(item, struct xa_node, private_list);
XA_STATE(xas, node->array, 0);
struct address_space *mapping;
struct radix_tree_node *node;
unsigned int i;
int ret;
/*
@ -421,14 +421,13 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
* the shadow node LRU under the i_pages lock and the
* lru_lock. Because the page cache tree is emptied before
* the inode can be destroyed, holding the lru_lock pins any
* address_space that has radix tree nodes on the LRU.
* address_space that has nodes on the LRU.
*
* We can then safely transition to the i_pages lock to
* pin only the address_space of the particular node we want
* to reclaim, take the node off-LRU, and drop the lru_lock.
*/
node = container_of(item, struct xa_node, private_list);
mapping = container_of(node->array, struct address_space, i_pages);
/* Coming from the list, invert the lock order */
@ -450,25 +449,17 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
goto out_invalid;
if (WARN_ON_ONCE(node->count != node->nr_values))
goto out_invalid;
for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
if (node->slots[i]) {
if (WARN_ON_ONCE(!xa_is_value(node->slots[i])))
goto out_invalid;
if (WARN_ON_ONCE(!node->nr_values))
goto out_invalid;
if (WARN_ON_ONCE(!mapping->nrexceptional))
goto out_invalid;
node->slots[i] = NULL;
node->nr_values--;
node->count--;
mapping->nrexceptional--;
}
}
if (WARN_ON_ONCE(node->nr_values))
goto out_invalid;
mapping->nrexceptional -= node->nr_values;
xas.xa_node = xa_parent_locked(&mapping->i_pages, node);
xas.xa_offset = node->offset;
xas.xa_shift = node->shift + XA_CHUNK_SHIFT;
xas_set_update(&xas, workingset_update_node);
/*
* We could store a shadow entry here which was the minimum of the
* shadow entries we were tracking ...
*/
xas_store(&xas, NULL);
inc_lruvec_page_state(virt_to_page(node), WORKINGSET_NODERECLAIM);
__radix_tree_delete_node(&mapping->i_pages, node,
workingset_lookup_update(mapping));
out_invalid:
xa_unlock_irq(&mapping->i_pages);