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Copy space can reserve some blocks for field-logging bits

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Useful for an oldgen
This commit is contained in:
Andy Wingo 2024-12-08 21:49:47 +01:00
parent a74a2c129c
commit b33efb2759
1 changed files with 72 additions and 2 deletions
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74
src/copy-space.h
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@ -118,6 +118,7 @@ struct copy_space_block_stack {
enum copy_space_flags {
COPY_SPACE_ATOMIC_FORWARDING = 1,
COPY_SPACE_ALIGNED = 2,
COPY_SPACE_HAS_FIELD_LOGGING_BITS = 4,
};
struct copy_space {
@ -645,6 +646,51 @@ copy_space_contains_address_aligned(struct copy_space *space, uintptr_t addr) {
return (addr - low_addr) < size;
}
static uint8_t*
copy_space_field_logged_byte(struct gc_edge edge) {
uintptr_t addr = gc_edge_address(edge);
uintptr_t base = align_down(addr, COPY_SPACE_SLAB_SIZE);
base += offsetof(struct copy_space_slab, blocks);
uintptr_t field = (addr & (COPY_SPACE_SLAB_SIZE - 1)) / sizeof(uintptr_t);
uintptr_t byte = field / 8;
return (uint8_t*) (base + field);
}
static uint8_t
copy_space_field_logged_bit(struct gc_edge edge) {
// Each byte has 8 bytes, covering 8 fields.
size_t field = gc_edge_address(edge) / sizeof(uintptr_t);
return 1 << (field % 8);
}
static int
copy_space_remember_edge(struct copy_space *space, struct gc_edge edge) {
GC_ASSERT(copy_space_contains_edge(space, edge));
uint8_t* loc = copy_space_field_logged_byte(edge);
uint8_t bit = copy_space_field_logged_bit(edge);
uint8_t byte = atomic_load_explicit(loc, memory_order_acquire);
do {
if (byte & bit) return 0;
} while (!atomic_compare_exchange_weak_explicit(loc, &byte, byte|bit,
memory_order_acq_rel,
memory_order_acquire));
return 1;
}
static int
copy_space_forget_edge(struct copy_space *space, struct gc_edge edge) {
GC_ASSERT(copy_space_contains_edge(space, edge));
uint8_t* loc = copy_space_field_logged_byte(edge);
uint8_t bit = copy_space_field_logged_bit(edge);
uint8_t byte = atomic_load_explicit(loc, memory_order_acquire);
do {
if (!(byte & bit)) return 0;
} while (!atomic_compare_exchange_weak_explicit(loc, &byte, byte&~bit,
memory_order_acq_rel,
memory_order_acquire));
return 1;
}
static inline void
copy_space_allocator_init(struct copy_space_allocator *alloc) {
memset(alloc, 0, sizeof(*alloc));
@ -703,6 +749,26 @@ copy_space_shrink(struct copy_space *space, size_t bytes) {
// can help us then!
}
static int
copy_space_has_field_logging_bits(struct copy_space *space) {
return space->flags & COPY_SPACE_HAS_FIELD_LOGGING_BITS;
}
static size_t
copy_space_field_logging_blocks(struct copy_space *space) {
if (!copy_space_has_field_logging_bits(space))
return 0;
size_t bytes = COPY_SPACE_SLAB_SIZE / sizeof (uintptr_t) / 8;
size_t blocks =
align_up(bytes, COPY_SPACE_BLOCK_SIZE) / COPY_SPACE_BLOCK_SIZE;
return blocks;
}
static size_t
copy_space_first_payload_block(struct copy_space *space) {
return copy_space_field_logging_blocks(space);
}
static void
copy_space_expand(struct copy_space *space, size_t bytes) {
GC_ASSERT(!copy_space_fixed_size(space));
@ -716,7 +782,9 @@ copy_space_expand(struct copy_space *space, size_t bytes) {
struct gc_lock lock = copy_space_lock(space);
for (size_t slab = 0; slab < nslabs; slab++) {
for (size_t idx = 0; idx < COPY_SPACE_NONHEADER_BLOCKS_PER_SLAB; idx++) {
for (size_t idx = copy_space_first_payload_block(space);
idx < COPY_SPACE_NONHEADER_BLOCKS_PER_SLAB;
idx++) {
struct copy_space_block *block = &slabs[slab].headers[idx];
block->all_zeroes[0] = block->all_zeroes[1] = 1;
block->in_core = 0;
@ -791,7 +859,9 @@ copy_space_init(struct copy_space *space, size_t size, uint32_t flags,
copy_space_add_slabs(space, slabs, nslabs);
struct gc_lock lock = copy_space_lock(space);
for (size_t slab = 0; slab < nslabs; slab++) {
for (size_t idx = 0; idx < COPY_SPACE_NONHEADER_BLOCKS_PER_SLAB; idx++) {
for (size_t idx = copy_space_first_payload_block(space);
idx < COPY_SPACE_NONHEADER_BLOCKS_PER_SLAB;
idx++) {
struct copy_space_block *block = &slabs[slab].headers[idx];
block->all_zeroes[0] = block->all_zeroes[1] = 1;
block->in_core = 0;