From 6be2792659d199a72cb7747ffeefe09a88cd4491 Mon Sep 17 00:00:00 2001
From: Ryan Fleury <ryan.j.fleury@gmail.com>
Date: Fri, 15 Nov 2024 14:40:05 -0800
Subject: [PATCH] search cache eviction

---
 src/dbgi/dbgi.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++--
 src/dbgi/dbgi.h |  4 ++++
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/src/dbgi/dbgi.c b/src/dbgi/dbgi.c
index 1c3a40be..24018adf 100644
--- a/src/dbgi/dbgi.c
+++ b/src/dbgi/dbgi.c
@@ -235,6 +235,7 @@ di_init(void)
     di_shared->search_threads[idx].ring_base  = push_array_no_zero(arena, U8, di_shared->search_threads[idx].ring_size);
     di_shared->search_threads[idx].thread = os_thread_launch(di_search_thread__entry_point, (void *)idx, 0);
   }
+  di_shared->search_evictor_thread = os_thread_launch(di_search_evictor_thread__entry_point, 0, 0);
 }
 
 ////////////////////////////////
@@ -667,7 +668,16 @@ di_search_items_from_key_params_query(DI_Scope *scope, U128 key, DI_SearchParams
       // rjf: no node? -> allocate
       if(node == 0)
       {
-        node = push_array(stripe->arena, DI_SearchNode, 1);
+        node = stripe->free_node;
+        if(node)
+        {
+          SLLStackPop(stripe->free_node);
+          MemoryZeroStruct(node);
+        }
+        else
+        {
+          node = push_array(stripe->arena, DI_SearchNode, 1);
+        }
         SLLQueuePush(slot->first, slot->last, node);
         node->key = key;
         for(U64 idx = 0; idx < ArrayCount(node->buckets); idx += 1)
@@ -677,7 +687,7 @@ di_search_items_from_key_params_query(DI_Scope *scope, U128 key, DI_SearchParams
       }
       
       // rjf: record update idx info
-      ins_atomic_u64_eval_assign(&node->last_update_tick_idx, update_tick_idx());
+      node->last_update_tick_idx = update_tick_idx();
       
       // rjf: try to grab last valid results for this key/query; determine if stale
       B32 stale = 1;
@@ -1347,6 +1357,7 @@ di_search_thread__entry_point(void *p)
         if(u128_match(n->key, key))
         {
           U64 bucket_idx = n->bucket_write_gen%ArrayCount(n->buckets);
+          n->work_refcount += 1;
           arena  = n->buckets[bucket_idx].arena;
           query  = push_str8_copy(scratch.arena, n->buckets[bucket_idx].query);
           params = di_search_params_copy(scratch.arena, &n->buckets[bucket_idx].params);
@@ -1453,6 +1464,7 @@ di_search_thread__entry_point(void *p)
             if(n->scope_refcount == 0)
             {
               n->bucket_read_gen += 1;
+              n->work_refcount -= 1;
               if(!cancelled)
               {
                 n->items = items;
@@ -1476,6 +1488,52 @@ di_search_thread__entry_point(void *p)
   }
 }
 
+internal void
+di_search_evictor_thread__entry_point(void *p)
+{
+  ThreadNameF("[di] search evictor thread");
+  for(;;)
+  {
+    for(U64 slot_idx = 0; slot_idx < di_shared->search_slots_count; slot_idx += 1)
+    {
+      U64 stripe_idx = slot_idx%di_shared->search_stripes_count;
+      DI_SearchSlot *slot = &di_shared->search_slots[slot_idx];
+      DI_SearchStripe *stripe = &di_shared->search_stripes[stripe_idx];
+      B32 slot_has_work = 0;
+      OS_MutexScopeR(stripe->rw_mutex)
+      {
+        for(DI_SearchNode *n = slot->first; n != 0; n = n->next)
+        {
+          if(n->last_update_tick_idx+10 < update_tick_idx() && n->scope_refcount == 0 && n->work_refcount == 0)
+          {
+            slot_has_work = 1;
+            break;
+          }
+        }
+      }
+      if(slot_has_work) OS_MutexScopeW(stripe->rw_mutex)
+      {
+        for(DI_SearchNode *n = slot->first, *next = 0; n != 0; n = next)
+        {
+          next = n->next;
+          if(n->last_update_tick_idx+10 < update_tick_idx() && n->scope_refcount == 0 && n->work_refcount == 0)
+          {
+            DLLRemove(slot->first, slot->last, n);
+            SLLStackPush(stripe->free_node, n);
+            for EachElement(idx, n->buckets)
+            {
+              arena_release(n->buckets[idx].arena);
+              MemoryZeroStruct(&n->buckets[idx]);
+            }
+            MemoryZeroStruct(&n->items);
+          }
+        }
+      }
+    }
+    os_sleep_milliseconds(100);
+  }
+}
+
 ////////////////////////////////
 //~ rjf: Match Store
 
diff --git a/src/dbgi/dbgi.h b/src/dbgi/dbgi.h
index fb2d76c9..3b3b23ea 100644
--- a/src/dbgi/dbgi.h
+++ b/src/dbgi/dbgi.h
@@ -185,6 +185,7 @@ struct DI_SearchNode
   DI_SearchNode *prev;
   U128 key;
   U64 scope_refcount;
+  U64 work_refcount;
   U64 last_update_tick_idx;
   U64 bucket_read_gen;
   U64 bucket_write_gen;
@@ -367,6 +368,7 @@ struct DI_Shared
   // rjf: search threads
   U64 search_threads_count;
   DI_SearchThread *search_threads;
+  OS_Handle search_evictor_thread;
 };
 
 ////////////////////////////////
@@ -457,6 +459,8 @@ ASYNC_WORK_DEF(di_search_work);
 internal int di_qsort_compare_search_items(DI_SearchItem *a, DI_SearchItem *b);
 internal void di_search_thread__entry_point(void *p);
 
+internal void di_search_evictor_thread__entry_point(void *p);
+
 ////////////////////////////////
 //~ rjf: Match Store