diff options
Diffstat (limited to 'libbcachefs/btree_types.h')
| -rw-r--r-- | libbcachefs/btree_types.h | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/libbcachefs/btree_types.h b/libbcachefs/btree_types.h index c0c16205..8b4df034 100644 --- a/libbcachefs/btree_types.h +++ b/libbcachefs/btree_types.h @@ -130,6 +130,42 @@ struct btree { #endif }; +struct btree_cache { + struct rhashtable table; + bool table_init_done; + /* + * We never free a struct btree, except on shutdown - we just put it on + * the btree_cache_freed list and reuse it later. This simplifies the + * code, and it doesn't cost us much memory as the memory usage is + * dominated by buffers that hold the actual btree node data and those + * can be freed - and the number of struct btrees allocated is + * effectively bounded. + * + * btree_cache_freeable effectively is a small cache - we use it because + * high order page allocations can be rather expensive, and it's quite + * common to delete and allocate btree nodes in quick succession. It + * should never grow past ~2-3 nodes in practice. + */ + struct mutex lock; + struct list_head live; + struct list_head freeable; + struct list_head freed; + + /* Number of elements in live + freeable lists */ + unsigned used; + unsigned reserve; + struct shrinker shrink; + + /* + * If we need to allocate memory for a new btree node and that + * allocation fails, we can cannibalize another node in the btree cache + * to satisfy the allocation - lock to guarantee only one thread does + * this at a time: + */ + struct task_struct *alloc_lock; + struct closure_waitlist alloc_wait; +}; + #define BTREE_FLAG(flag) \ static inline bool btree_node_ ## flag(struct btree *b) \ { return test_bit(BTREE_NODE_ ## flag, &b->flags); } \ |