extstore: prefill global page pool with extstore

the slab page mover algo would fill memory to evicting for a few seconds
before jumping to life and shoveling some pages into the global pool.

swore I was going to fix this post-release, but I had a moment of inspiration
after finding some code from another branch that did half the work. After a
bunch of stupid bugs it seems to work.

-o slab_automove_freeratio=0.N is now an option. This is *percentage of total
memory*, so don't set it too high.

1 files changed, 14 insertions, 1 deletions

diff --git a/slabs.c b/slabs.c
index c9a37aa..cedb1e8 100644
--- a/slabs.c
+++ b/slabs.c
@@ -62,6 +62,7 @@ static pthread_mutex_t slabs_rebalance_lock = PTHREAD_MUTEX_INITIALIZER;
 /*
  * Forward Declarations
  */
+static int grow_slab_list (const unsigned int id);
 static int do_slabs_newslab(const unsigned int id);
 static void *memory_allocate(size_t size);
 static void do_slabs_free(void *ptr, const size_t size, unsigned int id);
@@ -165,6 +166,19 @@ void slabs_init(const size_t limit, const double factor, const bool prealloc, co
     }
 }
 
+void slabs_prefill_global(void) {
+    void *ptr;
+    slabclass_t *p = &slabclass[0];
+    int len = settings.slab_page_size;
+
+    while (mem_malloced < mem_limit
+            && (ptr = memory_allocate(len)) != NULL) {
+        grow_slab_list(0);
+        p->slab_list[p->slabs++] = ptr;
+    }
+    mem_limit_reached = true;
+}
+
 static void slabs_preallocate (const unsigned int maxslabs) {
     int i;
     unsigned int prealloc = 0;
@@ -185,7 +199,6 @@ static void slabs_preallocate (const unsigned int maxslabs) {
             exit(1);
         }
     }
-
 }
 
 static int grow_slab_list (const unsigned int id) {