cap the number of GC threads to number of cpu cores

JuliaLang · Nov 16, 2023 · 1179c8e · 1179c8e
1 parent 7f18f76
commit 1179c8e
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/src/threading.c b/src/threading.c
@@ -709,6 +709,13 @@ void jl_init_threading(void)
             else {
                 jl_n_markthreads = (nthreads / 2) - 1;
             }
+            // if `--gcthreads` or ENV[NUM_GCTHREADS_NAME] was not specified,
+            // cap the number of threads that may run the mark phase to
+            // the number of CPU cores
+            int cpu = jl_cpu_threads();
+            if (jl_n_markthreads + 1 >= cpu) {
+                jl_n_markthreads = cpu - 1;
+            }
         }
     }
     int16_t ngcthreads = jl_n_markthreads + jl_n_sweepthreads;