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xarray: Replace exceptional entries

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Introduce xarray value entries and tagged pointers to replace radix
tree exceptional entries.  This is a slight change in encoding to allow
the use of an extra bit (we can now store BITS_PER_LONG - 1 bits in a
value entry).  It is also a change in emphasis; exceptional entries are
intimidating and different.  As the comment explains, you can choose
to store values or pointers in the xarray and they are both first-class
citizens.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
This commit is contained in:
Matthew Wilcox
2017-11-03 13:30:42 -04:00
parent 66ee620f06
commit 3159f943aa
26 changed files with 278 additions and 232 deletions
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13
mm/workingset.c
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@@ -155,8 +155,8 @@
* refault distance will immediately activate the refaulting page.
*/
#define EVICTION_SHIFT (RADIX_TREE_EXCEPTIONAL_ENTRY + \
NODES_SHIFT + \
#define EVICTION_SHIFT ((BITS_PER_LONG - BITS_PER_XA_VALUE) + \
NODES_SHIFT + \
MEM_CGROUP_ID_SHIFT)
#define EVICTION_MASK (~0UL >> EVICTION_SHIFT)
@@ -173,20 +173,19 @@ static unsigned int bucket_order __read_mostly;
static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction)
{
eviction >>= bucket_order;
eviction &= EVICTION_MASK;
eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid;
eviction = (eviction << NODES_SHIFT) | pgdat->node_id;
eviction = (eviction << RADIX_TREE_EXCEPTIONAL_SHIFT);
return (void *)(eviction | RADIX_TREE_EXCEPTIONAL_ENTRY);
return xa_mk_value(eviction);
}
static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat,
unsigned long *evictionp)
{
unsigned long entry = (unsigned long)shadow;
unsigned long entry = xa_to_value(shadow);
int memcgid, nid;
entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT;
nid = entry & ((1UL << NODES_SHIFT) - 1);
entry >>= NODES_SHIFT;
memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1);
@@ -453,7 +452,7 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
goto out_invalid;
for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
if (node->slots[i]) {
if (WARN_ON_ONCE(!radix_tree_exceptional_entry(node->slots[i])))
if (WARN_ON_ONCE(!xa_is_value(node->slots[i])))
goto out_invalid;
if (WARN_ON_ONCE(!node->exceptional))
goto out_invalid;