// TODO waste less memory; currently requires that all entries in alloc_table have a corresponding block in pool
void gc_init(void *start, void *end) {
// align end pointer on block boundary
end = (void*)((machine_uint_t)end & (~(BYTES_PER_BLOCK - 1)));
DEBUG_printf("Initializing GC heap: %p-%p\n", start, end);
// calculate parameters for GC
machine_uint_t total_word_len = (machine_uint_t*)end - (machine_uint_t*)start;
gc_alloc_table_byte_len = total_word_len * BYTES_PER_WORD / (1 + BITS_PER_BYTE / 2 * BYTES_PER_BLOCK);
gc_alloc_table_start = (byte*)start;
machine_uint_t gc_pool_block_len = gc_alloc_table_byte_len * BITS_PER_BYTE / 2;
machine_uint_t gc_pool_word_len = gc_pool_block_len * WORDS_PER_BLOCK;
gc_pool_start = (machine_uint_t*)end - gc_pool_word_len;
gc_pool_end = end;
// clear ATBs
memset(gc_alloc_table_start, 0, gc_alloc_table_byte_len);
// allocate first block because gc_pool_start points there and it will never
// be freed, so allocating 1 block with null pointers will minimise memory loss
ATB_FREE_TO_HEAD(0);
for (int i = 0; i < WORDS_PER_BLOCK; i++) {
gc_pool_start[i] = 0;
}
DEBUG_printf("GC layout:\n");
DEBUG_printf(" alloc table at %p, length %u bytes\n", gc_alloc_table_start, gc_alloc_table_byte_len);
DEBUG_printf(" pool at %p, length %u blocks = %u words = %u bytes\n", gc_pool_start, gc_pool_block_len, gc_pool_word_len, gc_pool_word_len * BYTES_PER_WORD);
}
// TODO waste less memory; currently requires that all entries in alloc_table have a corresponding block in pool
void gc_init(void *start, void *end) {
// align end pointer on block boundary
end = (void*)((mp_uint_t)end & (~(BYTES_PER_BLOCK - 1)));
DEBUG_printf("Initializing GC heap: %p..%p = " UINT_FMT " bytes\n", start, end, (byte*)end - (byte*)start);
// calculate parameters for GC (T=total, A=alloc table, F=finaliser table, P=pool; all in bytes):
// T = A + F + P
// F = A * BLOCKS_PER_ATB / BLOCKS_PER_FTB
// P = A * BLOCKS_PER_ATB * BYTES_PER_BLOCK
// => T = A * (1 + BLOCKS_PER_ATB / BLOCKS_PER_FTB + BLOCKS_PER_ATB * BYTES_PER_BLOCK)
mp_uint_t total_byte_len = (byte*)end - (byte*)start;
#if MICROPY_ENABLE_FINALISER
gc_alloc_table_byte_len = total_byte_len * BITS_PER_BYTE / (BITS_PER_BYTE + BITS_PER_BYTE * BLOCKS_PER_ATB / BLOCKS_PER_FTB + BITS_PER_BYTE * BLOCKS_PER_ATB * BYTES_PER_BLOCK);
#else
gc_alloc_table_byte_len = total_byte_len / (1 + BITS_PER_BYTE / 2 * BYTES_PER_BLOCK);
#endif
gc_alloc_table_start = (byte*)start;
#if MICROPY_ENABLE_FINALISER
mp_uint_t gc_finaliser_table_byte_len = (gc_alloc_table_byte_len * BLOCKS_PER_ATB + BLOCKS_PER_FTB - 1) / BLOCKS_PER_FTB;
gc_finaliser_table_start = gc_alloc_table_start + gc_alloc_table_byte_len;
#endif
mp_uint_t gc_pool_block_len = gc_alloc_table_byte_len * BLOCKS_PER_ATB;
gc_pool_start = (mp_uint_t*)((byte*)end - gc_pool_block_len * BYTES_PER_BLOCK);
gc_pool_end = (mp_uint_t*)end;
#if MICROPY_ENABLE_FINALISER
assert((byte*)gc_pool_start >= gc_finaliser_table_start + gc_finaliser_table_byte_len);
#endif
// clear ATBs
memset(gc_alloc_table_start, 0, gc_alloc_table_byte_len);
#if MICROPY_ENABLE_FINALISER
// clear FTBs
memset(gc_finaliser_table_start, 0, gc_finaliser_table_byte_len);
#endif
// allocate first block because gc_pool_start points there and it will never
// be freed, so allocating 1 block with null pointers will minimise memory loss
ATB_FREE_TO_HEAD(0);
for (int i = 0; i < WORDS_PER_BLOCK; i++) {
gc_pool_start[i] = 0;
}
// set last free ATB index to start of heap
gc_last_free_atb_index = 0;
// unlock the GC
gc_lock_depth = 0;
DEBUG_printf("GC layout:\n");
DEBUG_printf(" alloc table at %p, length " UINT_FMT " bytes, " UINT_FMT " blocks\n", gc_alloc_table_start, gc_alloc_table_byte_len, gc_alloc_table_byte_len * BLOCKS_PER_ATB);
#if MICROPY_ENABLE_FINALISER
DEBUG_printf(" finaliser table at %p, length " UINT_FMT " bytes, " UINT_FMT " blocks\n", gc_finaliser_table_start, gc_finaliser_table_byte_len, gc_finaliser_table_byte_len * BLOCKS_PER_FTB);
#endif
DEBUG_printf(" pool at %p, length " UINT_FMT " bytes, " UINT_FMT " blocks\n", gc_pool_start, gc_pool_block_len * BYTES_PER_BLOCK, gc_pool_block_len);
}
void *gc_alloc(machine_uint_t n_bytes) {
machine_uint_t n_blocks = ((n_bytes + BYTES_PER_BLOCK - 1) & (~(BYTES_PER_BLOCK - 1))) / BYTES_PER_BLOCK;
DEBUG_printf("gc_alloc(%u bytes -> %u blocks)\n", n_bytes, n_blocks);
// check for 0 allocation
if (n_blocks == 0) {
return NULL;
}
machine_uint_t i;
machine_uint_t end_block;
machine_uint_t start_block;
machine_uint_t n_free = 0;
int collected = 0;
for (;;) {
// look for a run of n_blocks available blocks
for (i = 0; i < gc_alloc_table_byte_len; i++) {
byte a = gc_alloc_table_start[i];
if (ATB_0_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 0; goto found; } } else { n_free = 0; }
if (ATB_1_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 1; goto found; } } else { n_free = 0; }
if (ATB_2_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 2; goto found; } } else { n_free = 0; }
if (ATB_3_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 3; goto found; } } else { n_free = 0; }
}
// nothing found!
if (collected) {
return NULL;
}
DEBUG_printf("gc_alloc(" UINT_FMT "): no free mem, triggering GC\n", n_bytes);
gc_collect();
collected = 1;
}
// found, ending at block i inclusive
found:
// get starting and end blocks, both inclusive
end_block = i;
start_block = i - n_free + 1;
// mark first block as used head
ATB_FREE_TO_HEAD(start_block);
// mark rest of blocks as used tail
// TODO for a run of many blocks can make this more efficient
for (machine_uint_t bl = start_block + 1; bl <= end_block; bl++) {
ATB_FREE_TO_TAIL(bl);
}
// return pointer to first block
return (void*)(gc_pool_start + start_block * WORDS_PER_BLOCK);
}
void *gc_alloc(machine_uint_t n_bytes, bool has_finaliser) {
machine_uint_t n_blocks = ((n_bytes + BYTES_PER_BLOCK - 1) & (~(BYTES_PER_BLOCK - 1))) / BYTES_PER_BLOCK;
DEBUG_printf("gc_alloc(" UINT_FMT " bytes -> " UINT_FMT " blocks)\n", n_bytes, n_blocks);
// check if GC is locked
if (gc_lock_depth > 0) {
return NULL;
}
// check for 0 allocation
if (n_blocks == 0) {
return NULL;
}
machine_uint_t i;
machine_uint_t end_block;
machine_uint_t start_block;
machine_uint_t n_free = 0;
int collected = 0;
for (;;) {
// look for a run of n_blocks available blocks
for (i = 0; i < gc_alloc_table_byte_len; i++) {
byte a = gc_alloc_table_start[i];
if (ATB_0_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 0; goto found; } } else { n_free = 0; }
if (ATB_1_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 1; goto found; } } else { n_free = 0; }
if (ATB_2_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 2; goto found; } } else { n_free = 0; }
if (ATB_3_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 3; goto found; } } else { n_free = 0; }
}
// nothing found!
if (collected) {
return NULL;
}
DEBUG_printf("gc_alloc(" UINT_FMT "): no free mem, triggering GC\n", n_bytes);
gc_collect();
collected = 1;
}
// found, ending at block i inclusive
found:
// get starting and end blocks, both inclusive
end_block = i;
start_block = i - n_free + 1;
// mark first block as used head
ATB_FREE_TO_HEAD(start_block);
// mark rest of blocks as used tail
// TODO for a run of many blocks can make this more efficient
for (machine_uint_t bl = start_block + 1; bl <= end_block; bl++) {
ATB_FREE_TO_TAIL(bl);
}
// get pointer to first block
void *ret_ptr = (void*)(gc_pool_start + start_block * WORDS_PER_BLOCK);
DEBUG_printf("gc_alloc(%p)\n", ret_ptr);
// 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((byte*)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
((mp_obj_base_t*)ret_ptr)->type = MP_OBJ_NULL;
// set mp_obj flag only if it has a finaliser
FTB_SET(start_block);
}
#endif
return ret_ptr;
}
void *gc_alloc(size_t n_bytes, bool has_finaliser) {
size_t n_blocks = ((n_bytes + BYTES_PER_BLOCK - 1) & (~(BYTES_PER_BLOCK - 1))) / BYTES_PER_BLOCK;
DEBUG_printf("gc_alloc(" UINT_FMT " bytes -> " UINT_FMT " blocks)\n", n_bytes, n_blocks);
// check if GC is locked
if (MP_STATE_MEM(gc_lock_depth) > 0) {
return NULL;
}
// check for 0 allocation
if (n_blocks == 0) {
return NULL;
}
size_t i;
size_t end_block;
size_t start_block;
size_t n_free = 0;
int collected = !MP_STATE_MEM(gc_auto_collect_enabled);
for (;;) {
// look for a run of n_blocks available blocks
for (i = MP_STATE_MEM(gc_last_free_atb_index); i < MP_STATE_MEM(gc_alloc_table_byte_len); i++) {
byte a = MP_STATE_MEM(gc_alloc_table_start)[i];
if (ATB_0_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 0; goto found; } } else { n_free = 0; }
if (ATB_1_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 1; goto found; } } else { n_free = 0; }
if (ATB_2_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 2; goto found; } } else { n_free = 0; }
if (ATB_3_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 3; goto found; } } else { n_free = 0; }
}
// nothing found!
if (collected) {
return NULL;
}
DEBUG_printf("gc_alloc(" UINT_FMT "): no free mem, triggering GC\n", n_bytes);
gc_collect();
collected = 1;
}
// found, ending at block i inclusive
found:
// get starting and end blocks, both inclusive
end_block = i;
start_block = i - n_free + 1;
// Set last free ATB index to block after last block we found, for start of
// next scan. To reduce fragmentation, we only do this if we were looking
// for a single free block, which guarantees that there are no free blocks
// before this one. Also, whenever we free or shink a block we must check
// if this index needs adjusting (see gc_realloc and gc_free).
if (n_free == 1) {
MP_STATE_MEM(gc_last_free_atb_index) = (i + 1) / BLOCKS_PER_ATB;
}
// mark first block as used head
ATB_FREE_TO_HEAD(start_block);
// mark rest of blocks as used tail
// TODO for a run of many blocks can make this more efficient
for (size_t bl = start_block + 1; bl <= end_block; bl++) {
ATB_FREE_TO_TAIL(bl);
}
// get pointer to first block
void *ret_ptr = (void*)(MP_STATE_MEM(gc_pool_start) + start_block * BYTES_PER_BLOCK);
DEBUG_printf("gc_alloc(%p)\n", ret_ptr);
// Zero out all the 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((byte*)ret_ptr, 0, (end_block - start_block + 1) * BYTES_PER_BLOCK);
#if MICROPY_ENABLE_FINALISER
if (has_finaliser) {
// clear type pointer in case it is never set
((mp_obj_base_t*)ret_ptr)->type = NULL;
// set mp_obj flag only if it has a finaliser
FTB_SET(start_block);
}
#else
(void)has_finaliser;
#endif
#if EXTENSIVE_HEAP_PROFILING
gc_dump_alloc_table();
#endif
return ret_ptr;
}
