From f1b660484ee296759ca427d966b3ffaafcead1e3 Mon Sep 17 00:00:00 2001 From: Andy Wingo Date: Fri, 7 Mar 2025 09:32:03 +0100 Subject: [PATCH] Remove gc_allocator_needs_clear Whether the returned object needs to be cleared or not depends on a couple things: - Whether the embedder actually needs the object to be cleared. - Whether the collector allocated the object from memory that was all zeroes already. The goal of course would be to prevent clearing memory if the mutator was just going to write all over it. But it's hard to know statically if the memory would have been all zeroes anyway, and in that case if you did clear it you'd be doing double work. In the end it's simpler to just require collectors to clear memory in bulk. We can revisit this later if it is an issue. --- api/bdw-attrs.h | 4 ---- api/gc-api.h | 10 ---------- api/gc-attrs.h | 2 -- api/mmc-attrs.h | 4 ---- api/pcc-attrs.h | 4 ---- api/semi-attrs.h | 4 ---- src/pcc.c | 1 - src/semi.c | 3 +-- 8 files changed, 1 insertion(+), 31 deletions(-) diff --git a/api/bdw-attrs.h b/api/bdw-attrs.h index 938356a5e..19d5250f2 100644 --- a/api/bdw-attrs.h +++ b/api/bdw-attrs.h @@ -36,10 +36,6 @@ static inline uint8_t gc_allocator_alloc_table_end_pattern(void) { GC_CRASH(); } -static inline int gc_allocator_needs_clear(void) { - return 0; -} - static inline enum gc_old_generation_check_kind gc_old_generation_check_kind(size_t) { return GC_OLD_GENERATION_CHECK_NONE; } diff --git a/api/gc-api.h b/api/gc-api.h index ff1a20927..58cd5c02d 100644 --- a/api/gc-api.h +++ b/api/gc-api.h @@ -56,14 +56,6 @@ GC_API_ void* gc_call_without_gc(struct gc_mutator *mut, void* (*f)(void*), GC_API_ void gc_collect(struct gc_mutator *mut, enum gc_collection_kind requested_kind); -static inline void gc_clear_fresh_allocation(struct gc_ref obj, - size_t size) GC_ALWAYS_INLINE; -static inline void gc_clear_fresh_allocation(struct gc_ref obj, - size_t size) { - if (!gc_allocator_needs_clear()) return; - memset(gc_ref_heap_object(obj), 0, size); -} - static inline void gc_update_alloc_table(struct gc_ref obj, size_t size) GC_ALWAYS_INLINE; static inline void gc_update_alloc_table(struct gc_ref obj, @@ -119,7 +111,6 @@ static inline void* gc_allocate_small_fast_bump_pointer(struct gc_mutator *mut, *hp_loc = new_hp; - gc_clear_fresh_allocation(gc_ref(hp), size); gc_update_alloc_table(gc_ref(hp), size); return (void*)hp; @@ -140,7 +131,6 @@ static inline void* gc_allocate_small_fast_freelist(struct gc_mutator *mut, size *freelist_loc = *(void**)head; - gc_clear_fresh_allocation(gc_ref_from_heap_object(head), size); gc_update_alloc_table(gc_ref_from_heap_object(head), size); return head; diff --git a/api/gc-attrs.h b/api/gc-attrs.h index f0a6e94e6..bb563c0e2 100644 --- a/api/gc-attrs.h +++ b/api/gc-attrs.h @@ -25,8 +25,6 @@ static inline size_t gc_allocator_alloc_table_alignment(void) GC_ALWAYS_INLINE; static inline uint8_t gc_allocator_alloc_table_begin_pattern(void) GC_ALWAYS_INLINE; static inline uint8_t gc_allocator_alloc_table_end_pattern(void) GC_ALWAYS_INLINE; -static inline int gc_allocator_needs_clear(void) GC_ALWAYS_INLINE; - enum gc_old_generation_check_kind { GC_OLD_GENERATION_CHECK_NONE, GC_OLD_GENERATION_CHECK_ALLOC_TABLE, diff --git a/api/mmc-attrs.h b/api/mmc-attrs.h index 65cb434c9..fe9edb0a4 100644 --- a/api/mmc-attrs.h +++ b/api/mmc-attrs.h @@ -36,10 +36,6 @@ static inline uint8_t gc_allocator_alloc_table_end_pattern(void) { return 16; } -static inline int gc_allocator_needs_clear(void) { - return 0; -} - static inline enum gc_old_generation_check_kind gc_old_generation_check_kind(size_t obj_size) { if (GC_GENERATIONAL) { if (obj_size <= gc_allocator_large_threshold()) diff --git a/api/pcc-attrs.h b/api/pcc-attrs.h index 654acf8b9..913208cdd 100644 --- a/api/pcc-attrs.h +++ b/api/pcc-attrs.h @@ -39,10 +39,6 @@ static inline uint8_t gc_allocator_alloc_table_end_pattern(void) { GC_CRASH(); } -static inline int gc_allocator_needs_clear(void) { - return 0; -} - static inline enum gc_old_generation_check_kind gc_old_generation_check_kind(size_t size) { if (!GC_GENERATIONAL) return GC_OLD_GENERATION_CHECK_NONE; diff --git a/api/semi-attrs.h b/api/semi-attrs.h index 69a87560e..b8baab693 100644 --- a/api/semi-attrs.h +++ b/api/semi-attrs.h @@ -28,10 +28,6 @@ static inline size_t gc_allocator_freelist_offset(size_t size) { GC_CRASH(); } -static inline int gc_allocator_needs_clear(void) { - return 1; -} - static inline size_t gc_allocator_alloc_table_alignment(void) { return 0; } diff --git a/src/pcc.c b/src/pcc.c index f3a94d22b..c480021f9 100644 --- a/src/pcc.c +++ b/src/pcc.c @@ -997,7 +997,6 @@ void* gc_allocate_slow(struct gc_mutator *mut, size_t size) { break; } - gc_clear_fresh_allocation(ret, size); return gc_ref_heap_object(ret); } diff --git a/src/semi.c b/src/semi.c index 0d0c9ecca..86541f913 100644 --- a/src/semi.c +++ b/src/semi.c @@ -437,6 +437,7 @@ static void collect(struct gc_mutator *mut, size_t for_alloc) { gc_heap_sizer_on_gc(heap->sizer, heap->size, live_size, pause_ns, resize_heap); reset_heap_limits(heap); + clear_memory(semi->hp, semi->limit - semi->hp); HEAP_EVENT(heap, restarting_mutators); // fprintf(stderr, "%zd bytes copied\n", (space->size>>1)-(space->limit-space->hp)); @@ -520,8 +521,6 @@ void* gc_allocate_slow(struct gc_mutator *mut, size_t size) { continue; } space->hp = new_hp; - // FIXME: Allow allocator to avoid clearing memory? - clear_memory(addr, size); return (void *)addr; } }