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Avoid redundant stat manipulation when moving spans. #468

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Avoid redundant stat manipulation when moving spans. #468

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8 changes: 8 additions & 0 deletions tcmalloc/central_freelist.h
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Original file line number Diff line number Diff line change
Expand Up @@ -517,8 +517,12 @@ inline Span* CentralFreeList<Forwarder>::ReleaseToSpans(
nonempty_.Add(span, cur_index);
span->set_nonempty_index(cur_index);
} else if (cur_index != prev_index) {
#ifdef TCMALLOC_INTERNAL_LEGACY_LOCKING
nonempty_.Remove(span, prev_index);
nonempty_.Add(span, cur_index);
#else
nonempty_.Move(span, prev_index, cur_index);
#endif
span->set_nonempty_index(cur_index);
}
return nullptr;
Expand Down Expand Up @@ -774,8 +778,12 @@ inline int CentralFreeList<Forwarder>::RemoveRange(absl::Span<void*> batch) {
const uint8_t cur_index =
IndexFor(span->is_long_lived_span(), cur_allocated, cur_bitwidth);
if (cur_index != prev_index) {
#ifdef TCMALLOC_INTERNAL_LEGACY_LOCKING
nonempty_.Remove(span, prev_index);
nonempty_.Add(span, cur_index);
#else
nonempty_.Move(span, prev_index, cur_index);
#endif
span->set_nonempty_index(cur_index);
}
}
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20 changes: 20 additions & 0 deletions tcmalloc/hinted_tracker_lists.h
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Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,26 @@ class HintedTrackerLists {
}
--size_;
}

// Moves pointer <pt> from list `from` to list `to`.
// REQUIRES: from < N && to < N && pt != nullptr
void Move(TrackerType* absl_nonnull pt TCMALLOC_CAPTURED_BY_THIS,
const size_t from, const size_t to) {
TC_ASSERT_LT(from, N);
TC_ASSERT_LT(to, N);
// This check is not strictly required, but we should avoid the linked list
// manipulations if we can.
TC_ASSERT_NE(from, to);
TC_ASSERT_NE(pt, nullptr);

if (lists_[from].remove(pt)) {
TC_ASSERT(nonempty_.GetBit(from));
nonempty_.ClearBit(from);
}
lists_[to].prepend(pt);
nonempty_.SetBit(to);
}

const TrackerList& operator[](const size_t n) const {
TC_ASSERT_LT(n, N);
return lists_[n];
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