ext4: introduce aging to extent status tree
Introduce a simple aging to extent status tree. Each extent has a
REFERENCED bit which gets set when the extent is used. Shrinker then
skips entries with referenced bit set and clears the bit. Thus
frequently used extents have higher chances of staying in memory.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 3059649..e04d457 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -382,7 +382,7 @@
static int ext4_es_can_be_merged(struct extent_status *es1,
struct extent_status *es2)
{
- if (ext4_es_status(es1) != ext4_es_status(es2))
+ if (ext4_es_type(es1) != ext4_es_type(es2))
return 0;
if (((__u64) es1->es_len) + es2->es_len > EXT_MAX_BLOCKS) {
@@ -425,6 +425,8 @@
es1 = rb_entry(node, struct extent_status, rb_node);
if (ext4_es_can_be_merged(es1, es)) {
es1->es_len += es->es_len;
+ if (ext4_es_is_referenced(es))
+ ext4_es_set_referenced(es1);
rb_erase(&es->rb_node, &tree->root);
ext4_es_free_extent(inode, es);
es = es1;
@@ -447,6 +449,8 @@
es1 = rb_entry(node, struct extent_status, rb_node);
if (ext4_es_can_be_merged(es, es1)) {
es->es_len += es1->es_len;
+ if (ext4_es_is_referenced(es1))
+ ext4_es_set_referenced(es);
rb_erase(node, &tree->root);
ext4_es_free_extent(inode, es1);
}
@@ -813,6 +817,8 @@
es->es_lblk = es1->es_lblk;
es->es_len = es1->es_len;
es->es_pblk = es1->es_pblk;
+ if (!ext4_es_is_referenced(es))
+ ext4_es_set_referenced(es);
stats->es_stats_cache_hits++;
} else {
stats->es_stats_cache_misses++;
@@ -1252,11 +1258,17 @@
* We can't reclaim delayed extent from status tree because
* fiemap, bigallic, and seek_data/hole need to use it.
*/
- if (!ext4_es_is_delayed(es)) {
- rb_erase(&es->rb_node, &tree->root);
- ext4_es_free_extent(inode, es);
- (*nr_shrunk)++;
+ if (ext4_es_is_delayed(es))
+ goto next;
+ if (ext4_es_is_referenced(es)) {
+ ext4_es_clear_referenced(es);
+ goto next;
}
+
+ rb_erase(&es->rb_node, &tree->root);
+ ext4_es_free_extent(inode, es);
+ (*nr_shrunk)++;
+next:
if (!node)
goto out_wrap;
es = rb_entry(node, struct extent_status, rb_node);