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[GC] Allow distribute_free_regions to decommit and redistribute #106414

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Merged
merged 2 commits into from
Aug 16, 2024
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[GC] Allow distribute_free_regions to decommit and redistribute #106414

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50ca0a2
Just the balance calculation change from #106168
markples Aug 14, 2024
96509d0
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markples Aug 14, 2024
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137 changes: 65 additions & 72 deletions src/coreclr/gc/gc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -13414,86 +13414,25 @@ void gc_heap::distribute_free_regions()
num_huge_region_units_to_consider[kind]));

// check if the free regions exceed the budget
// if so, put the highest free regions on the decommit list
// if so, consider putting the highest free regions on the decommit list
total_num_free_regions[kind] += num_regions_to_decommit[kind];

ptrdiff_t balance = total_num_free_regions[kind] + num_huge_region_units_to_consider[kind] - total_budget_in_region_units[kind];

// Ignore young huge regions if they are contributing to a surplus.
if (balance > 0)
{
if (balance > static_cast<ptrdiff_t>(num_young_huge_region_units_to_consider[kind]))
{
balance -= num_young_huge_region_units_to_consider[kind];
}
else
{
balance = 0;
}
}

if (
// first check if we should decommit any regions
if ((balance > 0)
#ifdef BACKGROUND_GC
(background_running_p() && (settings.condemned_generation != max_generation)) ||
&& (!background_running_p() || (settings.condemned_generation == max_generation))
#endif
(balance < 0))
)
{
dprintf (REGIONS_LOG, ("distributing the %zd %s regions deficit", -balance, kind_name[kind]));
// ignore young huge regions when determining how much to decommit
num_regions_to_decommit[kind] =
max(static_cast<ptrdiff_t>(0),
(balance - static_cast<ptrdiff_t>(num_young_huge_region_units_to_consider[kind])));

balance -= num_regions_to_decommit[kind];

#ifdef MULTIPLE_HEAPS
// we may have a deficit or - if background GC is going on - a surplus.
// adjust the budget per heap accordingly
if (balance != 0)
{
ptrdiff_t curr_balance = 0;
ptrdiff_t rem_balance = 0;
for (int i = 0; i < n_heaps; i++)
{
curr_balance += balance;
ptrdiff_t adjustment_per_heap = curr_balance / n_heaps;
curr_balance -= adjustment_per_heap * n_heaps;
ptrdiff_t new_budget = (ptrdiff_t)heap_budget_in_region_units[i][kind] + adjustment_per_heap;
ptrdiff_t min_budget = (kind == basic_free_region) ? (ptrdiff_t)min_heap_budget_in_region_units[i] : 0;
dprintf (REGIONS_LOG, ("adjusting the budget for heap %d from %zd %s regions by %zd to %zd",
i,
heap_budget_in_region_units[i][kind],
kind_name[kind],
adjustment_per_heap,
max (min_budget, new_budget)));
heap_budget_in_region_units[i][kind] = max (min_budget, new_budget);
rem_balance += new_budget - heap_budget_in_region_units[i][kind];
}
assert (rem_balance <= 0);
dprintf (REGIONS_LOG, ("remaining balance: %zd %s regions", rem_balance, kind_name[kind]));

// if we have a left over deficit, distribute that to the heaps that still have more than the minimum
while (rem_balance < 0)
{
for (int i = 0; i < n_heaps; i++)
{
size_t min_budget = (kind == basic_free_region) ? min_heap_budget_in_region_units[i] : 0;
if (heap_budget_in_region_units[i][kind] > min_budget)
{
dprintf (REGIONS_LOG, ("adjusting the budget for heap %d from %zd %s regions by %d to %zd",
i,
heap_budget_in_region_units[i][kind],
kind_name[kind],
-1,
heap_budget_in_region_units[i][kind] - 1));

heap_budget_in_region_units[i][kind] -= 1;
rem_balance += 1;
if (rem_balance == 0)
break;
}
}
}
}
#endif //MULTIPLE_HEAPS
}
else
{
num_regions_to_decommit[kind] = balance;
dprintf(REGIONS_LOG, ("distributing the %zd %s regions, removing %zd regions",
total_budget_in_region_units[kind],
kind_name[kind],
Expand Down Expand Up @@ -13527,6 +13466,60 @@ void gc_heap::distribute_free_regions()
}
}
}

#ifdef MULTIPLE_HEAPS
if (balance != 0)
{
dprintf (REGIONS_LOG, ("distributing the %zd %s regions deficit", -balance, kind_name[kind]));

// we may have a deficit or - if background GC is going on - a surplus.
// adjust the budget per heap accordingly

ptrdiff_t curr_balance = 0;
ptrdiff_t rem_balance = 0;
for (int i = 0; i < n_heaps; i++)
{
curr_balance += balance;
ptrdiff_t adjustment_per_heap = curr_balance / n_heaps;
curr_balance -= adjustment_per_heap * n_heaps;
ptrdiff_t new_budget = (ptrdiff_t)heap_budget_in_region_units[i][kind] + adjustment_per_heap;
ptrdiff_t min_budget = (kind == basic_free_region) ? (ptrdiff_t)min_heap_budget_in_region_units[i] : 0;
dprintf (REGIONS_LOG, ("adjusting the budget for heap %d from %zd %s regions by %zd to %zd",
i,
heap_budget_in_region_units[i][kind],
kind_name[kind],
adjustment_per_heap,
max (min_budget, new_budget)));
heap_budget_in_region_units[i][kind] = max (min_budget, new_budget);
rem_balance += new_budget - heap_budget_in_region_units[i][kind];
}
assert (rem_balance <= 0);
dprintf (REGIONS_LOG, ("remaining balance: %zd %s regions", rem_balance, kind_name[kind]));

// if we have a left over deficit, distribute that to the heaps that still have more than the minimum
while (rem_balance < 0)
{
for (int i = 0; i < n_heaps; i++)
{
size_t min_budget = (kind == basic_free_region) ? min_heap_budget_in_region_units[i] : 0;
if (heap_budget_in_region_units[i][kind] > min_budget)
{
dprintf (REGIONS_LOG, ("adjusting the budget for heap %d from %zd %s regions by %d to %zd",
i,
heap_budget_in_region_units[i][kind],
kind_name[kind],
-1,
heap_budget_in_region_units[i][kind] - 1));

heap_budget_in_region_units[i][kind] -= 1;
rem_balance += 1;
if (rem_balance == 0)
break;
}
}
}
}
#endif
}

for (int kind = basic_free_region; kind < kind_count; kind++)
Expand Down