Re: [PR] GH-40646: [C++] Re-order loads and stores in MemoryPoolStats update [arrow]

["pitrou (via GitHub)" <gi...@apache.org>]

pitrou commented on code in PR #40647:
URL: https://github.com/apache/arrow/pull/40647#discussion_r1532223016


##########
cpp/src/arrow/memory_pool.h:
##########
@@ -35,44 +36,62 @@ namespace internal {
 ///////////////////////////////////////////////////////////////////////
 // Helper tracking memory statistics
 
-class MemoryPoolStats {
- public:
-  MemoryPoolStats() : bytes_allocated_(0), max_memory_(0) {}
-
-  int64_t max_memory() const { return max_memory_.load(); }
-
-  int64_t bytes_allocated() const { return bytes_allocated_.load(); }
-
-  int64_t total_bytes_allocated() const { return total_allocated_bytes_.load(); }
+class alignas(/*CacheLineSize=*/64) MemoryPoolStats {

Review Comment:
   Is it so that all atomics end up on the same cache line? Perhaps add a comment.



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