From cdbb9b8555b4ddcc4c557f25ad785cae6209478d Mon Sep 17 00:00:00 2001 From: Peter Zhu Date: Wed, 20 Jul 2022 13:29:34 -0400 Subject: [PATCH] [Bug #18929] Fix heap creation thrashing in GC Before this commit, if we don't have enough slots after sweeping but had pages on the tomb heap, then the GC would frequently allocate and deallocate pages. This is because after sweeping it would set allocatable pages (since there were not enough slots) but free the pages on the tomb heap. This commit reuses pages on the tomb heap if there's not enough slots after sweeping. --- gc.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/gc.c b/gc.c index 4f92c371be52db..4b619fd33fe6e4 100644 --- a/gc.c +++ b/gc.c @@ -5810,6 +5810,19 @@ gc_sweep_finish_size_pool(rb_objspace_t *objspace, rb_size_pool_t *size_pool) min_free_slots = gc_params.heap_init_slots; } + /* If we don't have enough slots and we have pages on the tomb heap, move + * pages from the tomb heap to the eden heap. This may prevent page + * creation thrashing (frequently allocating and deallocting pages) and + * GC thrashing (running GC more frequently than required). */ + struct heap_page *resurrected_page; + while (swept_slots < min_free_slots && + (resurrected_page = heap_page_resurrect(objspace, size_pool))) { + swept_slots += resurrected_page->free_slots; + + heap_add_page(objspace, size_pool, heap, resurrected_page); + heap_add_freepage(heap, resurrected_page); + } + if (swept_slots < min_free_slots) { bool grow_heap = is_full_marking(objspace);