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py, gc: Only zero out the extra bytes at the end of the heap chunk. 

This is a small optimisation to zero out only the additional bytes that
the caller did not ask for.
This commit is contained in:
Damien George 2014-04-26 22:23:42 +01:00
parent dbc81df5d4
commit 32bef315be
2 changed files with 6 additions and 10 deletions
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12
py/gc.c
View File

@ -366,17 +366,17 @@ found:
// get pointer to first block
void *ret_ptr = (void*)(gc_pool_start + start_block * WORDS_PER_BLOCK);
// zero out the newly allocated blocks
// zero out the additional bytes of the newly allocated blocks
// This is needed because the blocks may have previously held pointers
// to the heap and will not be set to something else if the caller
// doesn't actually use the entire block. As such they will continue
// to point to the heap and may prevent other blocks from being reclaimed.
memset(ret_ptr, 0, (end_block - start_block + 1) * BYTES_PER_BLOCK);
memset(ret_ptr + n_bytes, 0, (end_block - start_block + 1) * BYTES_PER_BLOCK - n_bytes);
#if MICROPY_ENABLE_FINALISER
if (has_finaliser) {
// clear type pointer in case it is never set (now done above in memset)
//((mp_obj_base_t*)ret_ptr)->type = MP_OBJ_NULL;
// clear type pointer in case it is never set
((mp_obj_base_t*)ret_ptr)->type = MP_OBJ_NULL;
// set mp_obj flag only if it has a finaliser
FTB_SET(start_block);
}
@ -534,8 +534,8 @@ void *gc_realloc(void *ptr_in, machine_uint_t n_bytes) {
ATB_FREE_TO_TAIL(bl);
}
// zero out the newly allocated blocks (see comment above in gc_alloc)
memset(ptr_in + n_blocks * BYTES_PER_BLOCK, 0, (new_blocks - n_blocks) * BYTES_PER_BLOCK);
// zero out the additional bytes of the newly allocated blocks (see comment above in gc_alloc)
memset(ptr_in + n_bytes, 0, new_blocks * BYTES_PER_BLOCK - n_bytes);
return ptr_in;
}

4
py/malloc.c
View File

@ -88,13 +88,9 @@ void *m_malloc_with_finaliser(int num_bytes) {
void *m_malloc0(int num_bytes) {
void *ptr = m_malloc(num_bytes);
#if MICROPY_ENABLE_GC
// the GC already zeros out all memory
#else
if (ptr != NULL) {
memset(ptr, 0, num_bytes);
}
#endif
return ptr;
}