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[release/7.0] Disable mark phase prefetching for segments #78925

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Merged
merged 1 commit into from
Nov 29, 2022
Merged

[release/7.0] Disable mark phase prefetching for segments #78925

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15 changes: 14 additions & 1 deletion src/coreclr/gc/gc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -24093,12 +24093,17 @@ BOOL ref_p (uint8_t* r)
return (straight_ref_p (r) || partial_object_p (r));
}

mark_queue_t::mark_queue_t() : curr_slot_index(0)
mark_queue_t::mark_queue_t()
#ifdef MARK_PHASE_PREFETCH
: curr_slot_index(0)
#endif //MARK_PHASE_PREFETCH
{
#ifdef MARK_PHASE_PREFETCH
for (size_t i = 0; i < slot_count; i++)
{
slot_table[i] = nullptr;
}
#endif //MARK_PHASE_PREFETCH
}

// place an object in the mark queue
Expand All @@ -24108,6 +24113,7 @@ mark_queue_t::mark_queue_t() : curr_slot_index(0)
FORCEINLINE
uint8_t *mark_queue_t::queue_mark(uint8_t *o)
{
#ifdef MARK_PHASE_PREFETCH
Prefetch (o);

// while the prefetch is taking effect, park our object in the queue
Expand All @@ -24120,6 +24126,9 @@ uint8_t *mark_queue_t::queue_mark(uint8_t *o)
curr_slot_index = (slot_index + 1) % slot_count;
if (old_o == nullptr)
return nullptr;
#else //MARK_PHASE_PREFETCH
uint8_t* old_o = o;
#endif //MARK_PHASE_PREFETCH

// this causes us to access the method table pointer of the old object
BOOL already_marked = marked (old_o);
Expand Down Expand Up @@ -24171,6 +24180,7 @@ uint8_t *mark_queue_t::queue_mark(uint8_t *o, int condemned_gen)
// returns nullptr if there is no such object
uint8_t* mark_queue_t::get_next_marked()
{
#ifdef MARK_PHASE_PREFETCH
size_t slot_index = curr_slot_index;
size_t empty_slot_count = 0;
while (empty_slot_count < slot_count)
Expand All @@ -24190,15 +24200,18 @@ uint8_t* mark_queue_t::get_next_marked()
}
empty_slot_count++;
}
#endif //MARK_PHASE_PREFETCH
return nullptr;
}

void mark_queue_t::verify_empty()
{
#ifdef MARK_PHASE_PREFETCH
for (size_t slot_index = 0; slot_index < slot_count; slot_index++)
{
assert(slot_table[slot_index] == nullptr);
}
#endif //MARK_PHASE_PREFETCH
}

void gc_heap::mark_object_simple1 (uint8_t* oo, uint8_t* start THREAD_NUMBER_DCL)
Expand Down
3 changes: 3 additions & 0 deletions src/coreclr/gc/gcpriv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,7 @@ inline void FATAL_GC_ERROR()
// + creates some ro segs
// We can add more mechanisms here.
//#define STRESS_REGIONS
#define MARK_PHASE_PREFETCH
#endif //USE_REGIONS

// FEATURE_STRUCTALIGN was added by Midori. In CLR we are not interested
Expand Down Expand Up @@ -1224,9 +1225,11 @@ enum bookkeeping_element

class mark_queue_t
{
#ifdef MARK_PHASE_PREFETCH
static const size_t slot_count = 16;
uint8_t* slot_table[slot_count];
size_t curr_slot_index;
#endif //MARK_PHASE_PREFETCH

public:
mark_queue_t();
Expand Down