Commit d5e7f6e3 authored by Damien George's avatar Damien George
Browse files

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
parent 13ec400f
......@@ -62,6 +62,7 @@ STATIC int gc_stack_overflow;
STATIC mp_uint_t gc_stack[STACK_SIZE];
STATIC mp_uint_t *gc_sp;
STATIC mp_uint_t gc_lock_depth;
STATIC mp_uint_t gc_last_free_atb_index;
// ATB = allocation table byte
// 0b00 = FREE -- free block
......@@ -156,6 +157,9 @@ void gc_init(void *start, void *end) {
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;
......@@ -304,6 +308,7 @@ void gc_collect_root(void **ptrs, mp_uint_t len) {
void gc_collect_end(void) {
gc_deal_with_stack_overflow();
gc_sweep();
gc_last_free_atb_index = 0;
gc_unlock();
}
......@@ -374,7 +379,14 @@ void *gc_alloc(mp_uint_t n_bytes, bool has_finaliser) {
for (;;) {
// look for a run of n_blocks available blocks
for (i = 0; i < gc_alloc_table_byte_len; i++) {
for (i = gc_last_free_atb_index; 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; }
}
for (i = 0; i < gc_last_free_atb_index; 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; }
......@@ -397,6 +409,9 @@ found:
end_block = i;
start_block = i - n_free + 1;
// set last free ATB index to last block we found, for start of next scan
gc_last_free_atb_index = i / BLOCKS_PER_ATB;
// mark first block as used head
ATB_FREE_TO_HEAD(start_block);
......
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