first pass at LRU maintainer thread

The basics work, but tests still do not pass.

A background thread wakes up once per second, or when signaled. It is signaled
if a slab class gets an allocation request and has fewer than N chunks free.

The background thread shuffles LRU's: HOT, WARM, COLD. HOT is where new items
exist. HOT and WARM flow into COLD. Active items in COLD flow back to WARM.
Evictions are pulled from COLD.

item_update's no longer do anything (and need to be fixed to tick it->time).
Items are reshuffled within or around LRU's as they reach the bottom.

Ratios of HOT/WARM memory are hardcoded, as are the low/high watermarks.
Thread is not fast enough right now, sets cannot block on it.

1 files changed, 3 insertions, 0 deletions

diff --git a/slabs.h b/slabs.h
index c649c06..012089d 100644
--- a/slabs.h
+++ b/slabs.h
@@ -33,6 +33,9 @@ bool get_stats(const char *stat_type, int nkey, ADD_STAT add_stats, void *c);
 /** Fill buffer with stats */ /*@null@*/
 void slabs_stats(ADD_STAT add_stats, void *c);
 
+/* Hints as to freespace in slab class */
+unsigned int slabs_available_chunks(unsigned int id, bool *mem_flag, unsigned int *total_chunks);
+
 int start_slab_maintenance_thread(void);
 void stop_slab_maintenance_thread(void);