[sgen] Fixes for max-heap-size option (mono/mono#18446)

* [sgen] Don't subtract twice the nursery size from max_heap_size

We were subtracting the nursery size when initializing max_heap_size as well as adding it to the allocated_heap when allocating the nursery (alloc_nursery).

* [sgen] Trigger collection if failing to allocate los section

If the memory governor says we are exceeding the max_heap_size by allocating a los section (1MB) for a new los object, attempt to clear some space by triggering a major collection, before completely bailing out.

Commit migrated from https://github.com/mono/mono/commit/d9db79b4b281afc5064921ff69a4bbbfb2c5f0e1

diff --git a/src/mono/mono/sgen/sgen-los.c b/src/mono/mono/sgen/sgen-los.c
index 45c8ad2..d2c4b20 100644 (file)
--- a/src/mono/mono/sgen/sgen-los.c
+++ b/src/mono/mono/sgen/sgen-los.c
@@ -304,8 +304,15 @@ get_los_section_memory (size_t size)
                return randomize_los_object_start (free_chunks, obj_size, size, LOS_CHUNK_SIZE);
        }
 
-       if (!sgen_memgov_try_alloc_space (LOS_SECTION_SIZE, SPACE_LOS))
-               return NULL;
+       if (!sgen_memgov_try_alloc_space (LOS_SECTION_SIZE, SPACE_LOS)) {
+               /*
+                * We failed to allocate a section due to exceeding max_heap_size.
+                * Trigger a major collection and try again.
+                */
+               sgen_ensure_free_space (LOS_SECTION_SIZE, GENERATION_OLD);
+               if (!sgen_memgov_try_alloc_space (LOS_SECTION_SIZE, SPACE_LOS))
+                       return NULL;
+       }
 
        section = (LOSSection *)sgen_alloc_os_memory_aligned (LOS_SECTION_SIZE, LOS_SECTION_SIZE, (SgenAllocFlags)(SGEN_ALLOC_HEAP | SGEN_ALLOC_ACTIVATE), NULL, MONO_MEM_ACCOUNT_SGEN_LOS);
 

diff --git a/src/mono/mono/sgen/sgen-memory-governor.c b/src/mono/mono/sgen/sgen-memory-governor.c
index c5c679b..85167e5 100644 (file)
--- a/src/mono/mono/sgen/sgen-memory-governor.c
+++ b/src/mono/mono/sgen/sgen-memory-governor.c
@@ -519,7 +519,7 @@ sgen_memgov_init (size_t max_heap, size_t soft_limit, gboolean debug_allowance,
                sgen_env_var_error (MONO_GC_PARAMS_NAME, "Setting to minimum.", "`max-heap-size` must be at least 4 times as large as `nursery size`.");
                max_heap = SGEN_DEFAULT_NURSERY_SIZE * 4;
        }
-       max_heap_size = max_heap - SGEN_DEFAULT_NURSERY_SIZE;
+       max_heap_size = max_heap;
 
        sgen_gc_info.total_available_memory_bytes = max_heap;