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Fix off-by-one slab prefetch offset in x86-64 TcmallocSlab::Pop. #672

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Fix off-by-one slab prefetch offset in x86-64 TcmallocSlab::Pop. #672

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6 changes: 3 additions & 3 deletions tcmalloc/internal/percpu_tcmalloc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -864,9 +864,9 @@ inline ABSL_ATTRIBUTE_ALWAYS_INLINE void* TcmallocSlab<NumClasses>::Pop(
TC_ASSERT(result);
TSANAcquire(result);

// The next pop will be from current-1, but because we prefetch the previous
// element we've already just read that, so prefetch current-2.
PrefetchSlabMemory(scratch + (current - 2) * sizeof(void*));
// The next pop will be from current-2, but because we prefetch the previous
// element we've already just read that, so prefetch current-3.
PrefetchSlabMemory(scratch + (current - 3) * sizeof(void*));
PrefetchNextObject(next);
return AssumeNotNull(result);
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