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Aug 15, 2025
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introduce a few configs for DATAS fine tuning #118762

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+ introduce a few configs for DATAS fine tuning
Aug 15, 2025
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Aug 15, 2025
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103 changes: 74 additions & 29 deletions src/coreclr/gc/gc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -44216,38 +44216,42 @@ void gc_heap::init_static_data()
{
size_t gen0_min_size = get_gen0_min_size();

size_t gen0_max_size =
#ifdef MULTIPLE_HEAPS
max ((size_t)6*1024*1024, min ( Align(soh_segment_size/2), (size_t)200*1024*1024));
#else //MULTIPLE_HEAPS
(
#ifdef BACKGROUND_GC
gc_can_use_concurrent ?
6*1024*1024 :
#endif //BACKGROUND_GC
max ((size_t)6*1024*1024, min ( Align(soh_segment_size/2), (size_t)200*1024*1024))
);
#endif //MULTIPLE_HEAPS

gen0_max_size = max (gen0_min_size, gen0_max_size);

if (heap_hard_limit)
{
size_t gen0_max_size_seg = soh_segment_size / 4;
dprintf (GTC_LOG, ("limit gen0 max %zd->%zd", gen0_max_size, gen0_max_size_seg));
gen0_max_size = min (gen0_max_size, gen0_max_size_seg);
}
size_t gen0_max_size = 0;

size_t gen0_max_size_config = (size_t)GCConfig::GetGCGen0MaxBudget();

if (gen0_max_size_config)
{
gen0_max_size = min (gen0_max_size, gen0_max_size_config);
gen0_max_size = gen0_max_size_config;

#ifdef FEATURE_EVENT_TRACE
gen0_max_budget_from_config = gen0_max_size;
#endif //FEATURE_EVENT_TRACE
}
else
{
gen0_max_size =
#ifdef MULTIPLE_HEAPS
max ((size_t)6 * 1024 * 1024, min (Align(soh_segment_size / 2), (size_t)200 * 1024 * 1024));
#else //MULTIPLE_HEAPS
(
#ifdef BACKGROUND_GC
gc_can_use_concurrent ?
6 * 1024 * 1024 :
#endif //BACKGROUND_GC
max ((size_t)6 * 1024 * 1024, min (Align(soh_segment_size / 2), (size_t)200 * 1024 * 1024))
);
#endif //MULTIPLE_HEAPS

gen0_max_size = max (gen0_min_size, gen0_max_size);

if (heap_hard_limit)
{
size_t gen0_max_size_seg = soh_segment_size / 4;
dprintf (GTC_LOG, ("limit gen0 max %zd->%zd", gen0_max_size, gen0_max_size_seg));
gen0_max_size = min (gen0_max_size, gen0_max_size_seg);
}
}

gen0_max_size = Align (gen0_max_size);
gen0_min_size = min (gen0_min_size, gen0_max_size);
Expand Down Expand Up @@ -44284,6 +44288,17 @@ void gc_heap::init_static_data()
static_data_table[i][0].max_size = gen0_max_size;
static_data_table[i][1].max_size = gen1_max_size;
}

#ifdef DYNAMIC_HEAP_COUNT
if (gc_heap::dynamic_adaptation_mode == dynamic_adaptation_to_application_sizes)
{
gc_heap::dynamic_heap_count_data.min_gen0_new_allocation = gen0_min_size;
if (gen0_max_size_config)
{
gc_heap::dynamic_heap_count_data.max_gen0_new_allocation = gen0_max_size;
}
}
#endif //DYNAMIC_HEAP_COUNT
}

bool gc_heap::init_dynamic_data()
Expand Down Expand Up @@ -49735,13 +49750,43 @@ HRESULT GCHeap::Initialize()
}
// This should be adjusted based on the target tcp. See comments in gcpriv.h
gc_heap::dynamic_heap_count_data.around_target_threshold = 10.0;
// This should really be set as part of computing static data and should take conserve_mem_setting into consideration.
gc_heap::dynamic_heap_count_data.max_gen0_new_allocation = Align (min (dd_max_size (gc_heap::g_heaps[0]->dynamic_data_of (0)), (size_t)(64 * 1024 * 1024)), get_alignment_constant (TRUE));
gc_heap::dynamic_heap_count_data.min_gen0_new_allocation = Align (dd_min_size (gc_heap::g_heaps[0]->dynamic_data_of (0)), get_alignment_constant (TRUE));

dprintf (6666, ("datas max gen0 budget %Id, min %Id",
gc_heap::dynamic_heap_count_data.max_gen0_new_allocation, gc_heap::dynamic_heap_count_data.min_gen0_new_allocation));
int gen0_growth_soh_ratio_percent = (int)GCConfig::GetGCDGen0GrowthPercent();
if (gen0_growth_soh_ratio_percent)
{
gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_percent = (int)GCConfig::GetGCDGen0GrowthPercent() * 0.01f;
}
// You can specify what sizes you want to allow DATAS to stay within wrt the SOH stable size.
// By default DATAS allows 10x this size for gen0 budget when the size is small, and 0.1x when the size is large.
int gen0_growth_min_permil = (int)GCConfig::GetGCDGen0GrowthMinFactor();
int gen0_growth_max_permil = (int)GCConfig::GetGCDGen0GrowthMaxFactor();
if (gen0_growth_min_permil)
{
gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_min = gen0_growth_min_permil * 0.001f;
}
if (gen0_growth_max_permil)
{
gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_max = gen0_growth_max_permil * 0.001f;
}

if (gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_min > gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_max)
{
log_init_error_to_host ("DATAS min permil for gen0 growth %d is greater than max %d, it needs to be lower",
gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_min, gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_max);
return E_FAIL;
}

GCConfig::SetGCDTargetTCP ((int)gc_heap::dynamic_heap_count_data.target_tcp);
GCConfig::SetGCDGen0GrowthPercent ((int)(gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_percent * 100.0f));
GCConfig::SetGCDGen0GrowthMinFactor ((int)(gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_min * 1000.0f));
GCConfig::SetGCDGen0GrowthMaxFactor ((int)(gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_max * 1000.0f));
dprintf (6666, ("DATAS gen0 growth multiplier will be adjusted by %d%%, cap %.3f-%.3f, min budget %Id, max %Id",
(int)GCConfig::GetGCDGen0GrowthPercent(),
gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_min, gc_heap::dynamic_heap_count_data.gen0_growth_soh_ratio_max,
gc_heap::dynamic_heap_count_data.min_gen0_new_allocation, gc_heap::dynamic_heap_count_data.max_gen0_new_allocation));
}

GCConfig::SetGCDynamicAdaptationMode (gc_heap::dynamic_adaptation_mode);
#endif //DYNAMIC_HEAP_COUNT
GCScan::GcRuntimeStructuresValid (TRUE);

Expand Down Expand Up @@ -52280,13 +52325,11 @@ size_t gc_heap::get_gen0_min_size()
gen0size = gen0size / 8 * 5;
}

#ifdef USE_REGIONS
#ifdef STRESS_REGIONS
// This is just so we can test allocation using more than one region on machines with very
// small caches.
gen0size = ((size_t)1 << min_segment_size_shr) * 3;
#endif //STRESS_REGIONS
#endif //USE_REGIONS

gen0size = Align (gen0size);

Expand Down Expand Up @@ -53883,6 +53926,8 @@ bool gc_heap::compute_memory_settings(bool is_initialization, uint32_t& nhp, uin
m_high_memory_load_th = min ((high_memory_load_th + 5), v_high_memory_load_th);
almost_high_memory_load_th = (high_memory_load_th > 5) ? (high_memory_load_th - 5) : 1; // avoid underflow of high_memory_load_th - 5

GCConfig::SetGCHighMemPercent (high_memory_load_th);

return true;
}

Expand Down
5 changes: 4 additions & 1 deletion src/coreclr/gc/gcconfig.h
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Original file line number Diff line number Diff line change
Expand Up @@ -98,7 +98,7 @@ class GCConfigStringHolder
"prefixed by the CPU group number. Example: Unix - 1,3,5,7-9,12, Windows - 0:1,1:7-9") \
INT_CONFIG (GCHighMemPercent, "GCHighMemPercent", "System.GC.HighMemoryPercent", 0, "The percent for GC to consider as high memory") \
INT_CONFIG (GCProvModeStress, "GCProvModeStress", NULL, 0, "Stress the provisional modes") \
INT_CONFIG (GCGen0MaxBudget, "GCGen0MaxBudget", NULL, 0, "Specifies the largest gen0 allocation budget") \
INT_CONFIG (GCGen0MaxBudget, "GCGen0MaxBudget", "System.GC.Gen0MaxBudget", 0, "Specifies the largest gen0 allocation budget") \
INT_CONFIG (GCGen1MaxBudget, "GCGen1MaxBudget", NULL, 0, "Specifies the largest gen1 allocation budget") \
INT_CONFIG (GCLowSkipRatio, "GCLowSkipRatio", NULL, 30, "Specifies the low generation skip ratio") \
INT_CONFIG (GCHeapHardLimit, "GCHeapHardLimit", "System.GC.HeapHardLimit", 0, "Specifies a hard limit for the GC heap") \
Expand Down Expand Up @@ -144,6 +144,9 @@ class GCConfigStringHolder
INT_CONFIG (GCDynamicAdaptationMode, "GCDynamicAdaptationMode", "System.GC.DynamicAdaptationMode", 1, "Enable the GC to dynamically adapt to application sizes.") \
INT_CONFIG (GCDTargetTCP, "GCDTargetTCP", "System.GC.DTargetTCP", 0, "Specifies the target tcp for DATAS") \
INT_CONFIG (GCDBGCRatio, "GCDBGCRatio", NULL, 0, "Specifies the ratio of BGC to NGC2 for HC change") \
INT_CONFIG (GCDGen0GrowthPercent, "GCDGen0GrowthPercent", "System.GC.DGen0GrowthPercent", 0, "Specifies the percentage of the default growth factor") \
INT_CONFIG (GCDGen0GrowthMinFactor, "GCDGen0GrowthMinFactor", "System.GC.DGen0GrowthMinFactor", 0, "Specifies the minimum growth factor in permil") \
INT_CONFIG (GCDGen0GrowthMaxFactor, "GCDGen0GrowthMaxFactor", "System.GC.DGen0GrowthMaxFactor", 0, "Specifies the maximum growth factor in permil") \
BOOL_CONFIG (GCCacheSizeFromSysConf, "GCCacheSizeFromSysConf", NULL, false, "Specifies using sysconf to retrieve the last level cache size for Unix.")

// This class is responsible for retreiving configuration information
Expand Down
30 changes: 21 additions & 9 deletions src/coreclr/gc/gcpriv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -4388,6 +4388,18 @@ class gc_heap
float target_tcp = 2.0;
float target_gen2_tcp = 10.0;

// The following 3 constants are used in the computation for the total gen0 budget relative to the stable soh size.
//
// By default DATAS computes a multiplier (gen0_growth_soh_ratio) that scales the size. This multiplier follows
// a power decay curve where the multiplier decreases rapidly as the size increases. We cap it at 10x at the low
// end and 10% at the high end.
//
// You can choose to modify these by specifying gen0_growth_factor_percent to reduce or increase this multiplier
// and the min/max multipliers.
float gen0_growth_soh_ratio_percent = 1.0;
float gen0_growth_soh_ratio_min = 0.1f;
float gen0_growth_soh_ratio_max = 10.0;

static const int recorded_adjustment_size = 4;
static const int sample_size = 3;
static const int recorded_tcp_array_size = 64;
Expand Down Expand Up @@ -5069,23 +5081,23 @@ class gc_heap
// time in msl).
//

size_t max_gen0_new_allocation;
size_t min_gen0_new_allocation;
size_t max_gen0_new_allocation = 64 * 1024 * 1024;
size_t min_gen0_new_allocation = 0;

size_t compute_total_gen0_budget (size_t total_soh_stable_size)
{
assert (total_soh_stable_size > 0);

float factor = (float)(20 - conserve_mem_setting);
double old_gen_growth_factor = factor / sqrt ((double)total_soh_stable_size / 1000.0 / 1000.0);
double saved_old_gen_growth_factor = old_gen_growth_factor;
old_gen_growth_factor = min (10.0, old_gen_growth_factor);
old_gen_growth_factor = max (0.1, old_gen_growth_factor);
float factor = (float)(20 - conserve_mem_setting) * gen0_growth_soh_ratio_percent;
double gen0_growth_soh_ratio = factor / sqrt ((double)total_soh_stable_size / 1000.0 / 1000.0);
double saved_gen0_growth_soh_ratio = gen0_growth_soh_ratio;
gen0_growth_soh_ratio = min ((double)gen0_growth_soh_ratio_max, gen0_growth_soh_ratio);
gen0_growth_soh_ratio = max ((double)gen0_growth_soh_ratio_min, gen0_growth_soh_ratio);

size_t total_new_allocation_old_gen = (size_t)(old_gen_growth_factor * (double)total_soh_stable_size);
size_t total_new_allocation_old_gen = (size_t)(gen0_growth_soh_ratio * (double)total_soh_stable_size);
dprintf (6666, ("stable soh %Id (%.3fmb), factor %.3f=>%.3f -> total gen0 new_alloc %Id (%.3fmb)",
total_soh_stable_size, ((double)total_soh_stable_size / 1000.0 / 1000.0),
saved_old_gen_growth_factor, old_gen_growth_factor, total_new_allocation_old_gen,
saved_gen0_growth_soh_ratio, gen0_growth_soh_ratio, total_new_allocation_old_gen,
((double)total_new_allocation_old_gen / 1000.0 / 1000.0)));
return total_new_allocation_old_gen;
}
Expand Down
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