Improve thrashing detection

src/gc.c

@@ -697,7 +697,7 @@ static uint64_t old_heap_size = 0;
 static uint64_t old_alloc_diff = 0;
 static uint64_t old_freed_diff = 0;
 static uint64_t gc_end_time = 0;
-
+static int thrash_counter = 0;
 
 // global variables for GC stats
 
@@ -3324,7 +3324,7 @@ static int _jl_gc_collect(jl_ptls_t ptls, jl_gc_collection_t collection)
         gc_num.last_incremental_sweep = gc_end_time;
     }
 
-    int thrashing = 0; // maybe we should report this to the user or error out?
+    int thrashing = thrash_counter > 4; // maybe we should report this to the user or error out?
     size_t heap_size = jl_atomic_load_relaxed(&gc_heap_stats.heap_size);
     double target_allocs = 0.0;
     double min_interval = default_collect_interval;
@@ -3343,7 +3343,10 @@ static int _jl_gc_collect(jl_ptls_t ptls, jl_gc_collection_t collection)
         old_freed_diff = freed_diff;
         old_pause_time = pause;
         old_heap_size = heap_size; // TODO: Update these values dynamically instead of just during the GC
-        thrashing = gc_time > mutator_time * 98 ? 1 : 0;
+        if (gc_time > alloc_time * 95)
+            thrash_counter += 1;
+        else
+            thrash_counter = 0;
         if (alloc_mem != 0 && alloc_time != 0 && gc_mem != 0 && gc_time != 0 ) {
             double alloc_rate = alloc_mem/alloc_time;
             double gc_rate = gc_mem/gc_time;