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8170817: G1: Returning MinTLABSize from unsafe_max_tlab_alloc causes TLAB flapping #16102

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8170817: G1: Returning MinTLABSize from unsafe_max_tlab_alloc causes TLAB flapping #16102

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9 changes: 6 additions & 3 deletions src/hotspot/share/gc/g1/g1Allocator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -191,11 +191,14 @@ size_t G1Allocator::unsafe_max_tlab_alloc() {
uint node_index = current_node_index();
HeapRegion* hr = mutator_alloc_region(node_index)->get();
size_t max_tlab = _g1h->max_tlab_size() * wordSize;
if (hr == nullptr) {

if (hr == nullptr || hr->free() < MinTLABSize) {
// The next TLAB allocation will most probably happen in a new region,
// therefore we can attempt to allocate the maximum allowed TLAB size.
return max_tlab;
} else {
return clamp(hr->free(), MinTLABSize, max_tlab);
}

return MIN2(hr->free(), max_tlab);
}

size_t G1Allocator::used_in_alloc_regions() {
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