[GitHub] [incubator-doris] xinyiZzz commented on a diff in pull request #9581: [Enhancement] [Memory] [Vectorized] Stress test and optimize memory allocation

[GitBox <gi...@apache.org>]

xinyiZzz commented on code in PR #9581:
URL: https://github.com/apache/incubator-doris/pull/9581#discussion_r873843542


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be/src/runtime/memory/chunk_allocator.cpp:
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@@ -219,6 +224,10 @@ void ChunkAllocator::free(const Chunk& chunk, MemTracker* tracker) {
         }
     } while (!_reserved_bytes.compare_exchange_weak(old_reserved_bytes, new_reserved_bytes));
 
+    // Reduce set metric frequency
+    if (_reserved_bytes % 100 == 32) {

Review Comment:
   At the first look, ChunkAllocator will allocate/free many times, the memory size of each allocate/free is a multiple of 2, so `_reserved_bytes% 100 == 32` will definitely happen, and the latest `_reserved_bytes` value will be set each time .
   
   The real-time and accurate `_reserved_bytes` value is not required. Usually, the value of `_reserved_bytes` is equal to ChunkAllocator MemTracker. The `_reserved_bytes` metric is only concerned when verifying the accuracy of MemTracker.
   
   Therefore, reduce the number of sets and reduce the performance impact.



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