예제 #1
0
파일: gc.c 프로젝트: un33k/micropython
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;
}
예제 #2
0
파일: gc.c 프로젝트: AvdN/micropython
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;
}