py: Speed up GC allocation.
This simple patch gives a very significant speed up for memory allocation with the GC. Eg, on PYBv1.0: tests/basics/dict_del.py: 3.55 seconds -> 1.19 seconds tests/misc/rge_sm.py: 15.3 seconds -> 2.48 seconds
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17
py/gc.c
17
py/gc.c
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@ -62,6 +62,7 @@ STATIC int gc_stack_overflow;
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STATIC mp_uint_t gc_stack[STACK_SIZE];
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STATIC mp_uint_t *gc_sp;
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STATIC mp_uint_t gc_lock_depth;
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STATIC mp_uint_t gc_last_free_atb_index;
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// ATB = allocation table byte
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// 0b00 = FREE -- free block
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@ -156,6 +157,9 @@ void gc_init(void *start, void *end) {
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gc_pool_start[i] = 0;
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}
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// set last free ATB index to start of heap
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gc_last_free_atb_index = 0;
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// unlock the GC
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gc_lock_depth = 0;
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@ -304,6 +308,7 @@ void gc_collect_root(void **ptrs, mp_uint_t len) {
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void gc_collect_end(void) {
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gc_deal_with_stack_overflow();
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gc_sweep();
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gc_last_free_atb_index = 0;
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gc_unlock();
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}
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@ -374,7 +379,14 @@ void *gc_alloc(mp_uint_t n_bytes, bool has_finaliser) {
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for (;;) {
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// look for a run of n_blocks available blocks
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for (i = 0; i < gc_alloc_table_byte_len; i++) {
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for (i = gc_last_free_atb_index; i < gc_alloc_table_byte_len; i++) {
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byte a = gc_alloc_table_start[i];
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if (ATB_0_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 0; goto found; } } else { n_free = 0; }
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if (ATB_1_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 1; goto found; } } else { n_free = 0; }
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if (ATB_2_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 2; goto found; } } else { n_free = 0; }
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if (ATB_3_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 3; goto found; } } else { n_free = 0; }
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}
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for (i = 0; i < gc_last_free_atb_index; i++) {
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byte a = gc_alloc_table_start[i];
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if (ATB_0_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 0; goto found; } } else { n_free = 0; }
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if (ATB_1_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 1; goto found; } } else { n_free = 0; }
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@ -397,6 +409,9 @@ found:
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end_block = i;
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start_block = i - n_free + 1;
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// set last free ATB index to last block we found, for start of next scan
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gc_last_free_atb_index = i / BLOCKS_PER_ATB;
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// mark first block as used head
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ATB_FREE_TO_HEAD(start_block);
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