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Added the ability to specify a Spin Count Unit via a GC Configuration #84339

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Merged
mrsharm merged 1 commit into from
Apr 6, 2023
Merged

Added the ability to specify a Spin Count Unit via a GC Configuration #84339

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29 changes: 22 additions & 7 deletions src/coreclr/gc/gc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,8 @@ BOOL bgc_heap_walk_for_etw_p = FALSE;

#define UOH_ALLOCATION_RETRY_MAX_COUNT 2

#define MAX_YP_SPIN_COUNT_UNIT 32768

uint32_t yp_spin_count_unit = 0;
uint32_t original_spin_count_unit = 0;
size_t loh_size_threshold = LARGE_OBJECT_SIZE;
Expand Down Expand Up @@ -2288,6 +2290,7 @@ double gc_heap::short_plugs_pad_ratio = 0;

int gc_heap::generation_skip_ratio_threshold = 0;
int gc_heap::conserve_mem_setting = 0;
bool gc_heap::spin_count_unit_config_p = false;

uint64_t gc_heap::suspended_start_time = 0;
uint64_t gc_heap::end_gc_time = 0;
Expand Down Expand Up @@ -13839,6 +13842,15 @@ HRESULT gc_heap::initialize_gc (size_t soh_segment_size,
yp_spin_count_unit = 32 * g_num_processors;
#endif //MULTIPLE_HEAPS

// Check if the values are valid for the spin count if provided by the user
// and if they are, set them as the yp_spin_count_unit and then ignore any updates made in SetYieldProcessorScalingFactor.
int64_t spin_count_unit_from_config = GCConfig::GetGCSpinCountUnit();
gc_heap::spin_count_unit_config_p = (spin_count_unit_from_config > 0) && (spin_count_unit_from_config <= MAX_YP_SPIN_COUNT_UNIT);
if (gc_heap::spin_count_unit_config_p)
{
yp_spin_count_unit = static_cast<int32_t>(spin_count_unit_from_config);
}

original_spin_count_unit = yp_spin_count_unit;

#if defined(__linux__)
Expand Down Expand Up @@ -45860,14 +45872,17 @@ size_t GCHeap::GetPromotedBytes(int heap_index)

void GCHeap::SetYieldProcessorScalingFactor (float scalingFactor)
{
assert (yp_spin_count_unit != 0);
uint32_t saved_yp_spin_count_unit = yp_spin_count_unit;
yp_spin_count_unit = (uint32_t)((float)original_spin_count_unit * scalingFactor / (float)9);

// It's very suspicious if it becomes 0 and also, we don't want to spin too much.
if ((yp_spin_count_unit == 0) || (yp_spin_count_unit > 32768))
if (!gc_heap::spin_count_unit_config_p)
{
yp_spin_count_unit = saved_yp_spin_count_unit;
assert (yp_spin_count_unit != 0);
uint32_t saved_yp_spin_count_unit = yp_spin_count_unit;
yp_spin_count_unit = (uint32_t)((float)original_spin_count_unit * scalingFactor / (float)9);

// It's very suspicious if it becomes 0 and also, we don't want to spin too much.
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@danmoseley danmoseley Apr 27, 2023

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if it's suspicious should it assert (yp_spin_count_unit != 0); again here

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@mrsharm mrsharm Apr 28, 2023

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Yes, it makes sense to assert once more. Will work on adding an additional protective assert.

if ((yp_spin_count_unit == 0) || (yp_spin_count_unit > MAX_YP_SPIN_COUNT_UNIT))
{
yp_spin_count_unit = saved_yp_spin_count_unit;
}
}
}

Expand Down
3 changes: 2 additions & 1 deletion src/coreclr/gc/gcconfig.h
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Expand Up @@ -136,7 +136,8 @@ class GCConfigStringHolder
INT_CONFIG (GCEnabledInstructionSets, "GCEnabledInstructionSets", NULL, -1, "Specifies whether GC can use AVX2 or AVX512F - 0 for neither, 1 for AVX2, 3 for AVX512F")\
INT_CONFIG (GCConserveMem, "GCConserveMemory", "System.GC.ConserveMemory", 0, "Specifies how hard GC should try to conserve memory - values 0-9") \
INT_CONFIG (GCWriteBarrier, "GCWriteBarrier", NULL, 0, "Specifies whether GC should use more precise but slower write barrier") \
STRING_CONFIG(GCName, "GCName", "System.GC.Name", "Specifies the path of the standalone GC implementation.")
STRING_CONFIG(GCName, "GCName", "System.GC.Name", "Specifies the path of the standalone GC implementation.") \
INT_CONFIG (GCSpinCountUnit, "GCSpinCountUnit", 0, 0, "Specifies the spin count unit used by the GC.")
// This class is responsible for retreiving configuration information
// for how the GC should operate.
class GCConfig
Expand Down
2 changes: 2 additions & 0 deletions src/coreclr/gc/gcpriv.h
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Expand Up @@ -4097,6 +4097,8 @@ class gc_heap
PER_HEAP_ISOLATED_FIELD_INIT_ONLY int generation_skip_ratio_threshold;
PER_HEAP_ISOLATED_FIELD_INIT_ONLY int conserve_mem_setting;

PER_HEAP_ISOLATED_FIELD_INIT_ONLY bool spin_count_unit_config_p;

// For SOH we always allocate segments of the same
// size unless no_gc_region requires larger ones.
PER_HEAP_ISOLATED_FIELD_INIT_ONLY size_t soh_segment_size;
Expand Down