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Don't use exchange in the hot path of the GC #50021

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Merged
merged 3 commits into from
Jun 8, 2023
Merged

Don't use exchange in the hot path of the GC #50021

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36ce0ee
Don't use exchange in the hot path of the GC
gbaraldi May 31, 2023
6fbdf3d
Save one extra load
gbaraldi Jun 1, 2023
267b3d6
Return a constant
gbaraldi Jun 1, 2023
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8 changes: 4 additions & 4 deletions src/gc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -804,7 +804,7 @@ STATIC_INLINE void gc_queue_big_marked(jl_ptls_t ptls, bigval_t *hdr,
FORCE_INLINE int gc_try_setmark_tag(jl_taggedvalue_t *o, uint8_t mark_mode) JL_NOTSAFEPOINT
{
assert(gc_marked(mark_mode));
uintptr_t tag = o->header;
uintptr_t tag = jl_atomic_load_relaxed((_Atomic(uintptr_t)*)&o->header);
if (gc_marked(tag))
return 0;
if (mark_reset_age) {
Expand All @@ -818,9 +818,9 @@ FORCE_INLINE int gc_try_setmark_tag(jl_taggedvalue_t *o, uint8_t mark_mode) JL_N
tag = tag | mark_mode;
assert((tag & 0x3) == mark_mode);
}
tag = jl_atomic_exchange_relaxed((_Atomic(uintptr_t)*)&o->header, tag);
verify_val(jl_valueof(o));
return !gc_marked(tag);
jl_atomic_store_relaxed((_Atomic(uintptr_t)*)&o->header, tag); //xchg here was slower than
verify_val(jl_valueof(o)); //potentially redoing work because of a stale tag.
return 1;
}

// This function should be called exactly once during marking for each big
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