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xo-gc: bugfix + mutation log test passes

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This commit is contained in:
Roland Conybeare 2026-04-19 19:57:49 -04:00
commit 362dcf73fc
6 changed files with 310 additions and 117 deletions
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20
src/gc/MutationLogStore.cpp
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@ -29,10 +29,10 @@ namespace xo {
for (std::uint32_t mlog_role = 0; mlog_role < c_n_role + 1; ++mlog_role) {
this->mlog_storage_[mlog_role][igen]
= _make_mlog(igen,
label_v[mlog_role],
config_.mutation_log_z_,
page_z);
= this->_make_mlog(igen,
label_v[mlog_role],
config_.mutation_log_z_,
page_z);
this->mlog_[mlog_role][igen]
= &(mlog_storage_[mlog_role][igen]);
@ -152,6 +152,8 @@ namespace xo {
*p_lhs = rhs;
if (!config_.enabled_flag_) {
log && log(xtag("msg", "noop b/c incremental gc disabled"));
// only need to log mutations when incremental gc is enabled
return;
}
@ -163,6 +165,8 @@ namespace xo {
Generation src_g = gco_store->generation_of(Role::to_space(), p_lhs);
if (src_g.is_sentinel()) {
log && log(xtag("msg", "noop because src not gc-owned"));
// only need mlog entries for gc-owned pointers.
// In this case pointer does not originate in gc-owned space
return;
@ -171,11 +175,15 @@ namespace xo {
Generation dest_g = gco_store->generation_of(Role::to_space(), rhs.data());
if (dest_g.is_sentinel()) {
log && log(xtag("msg", "noop because dest not gc-owned"));
// similarly, don't need mlog entry to non-gc-owned destination
return;
}
if (src_g < dest_g) {
log && log(xtag("msg", "noop because src gen younger than dest gen"));
// young-to-old pointers don't need to be remembered,
// since a GC cycle that collects an (old) generation is guarnatted
// to also collect all younger generations.
@ -194,6 +202,8 @@ namespace xo {
assert(src_hdr && dest_hdr);
if (gco_store->header2age(*src_hdr) <= gco_store->header2age(*dest_hdr)) {
log && log(xtag("msg", "noop because src age no older than dest age"));
// source and destination have the same age;
// therefore are always collected on the same set of GC cycles
// -> no need to remember separately.
@ -258,7 +268,7 @@ namespace xo {
// - to_mlog, triage_mlog are empty
for (Generation child_gen{0};
child_gen + 2 < config_.n_generation_;
child_gen + 1 < config_.n_generation_;
++child_gen) {
MutationLog * from_mlog = this->mlog_[Role::from_space()][child_gen];