relax memory ordering: we can use std::memory_order_relaxed for statistics

Author: kolomenkin

DataEngine.cpp

@@ -10,15 +10,15 @@ std::optional<DataEngine::ExtendedValue> DataEngine::get(const std::string_view
     const auto iter = m_data.find(strName);
     if (iter == m_data.cend())
     {
-        m_reads.fetch_add(1, std::memory_order_acq_rel);
+        m_reads.fetch_add(1, std::memory_order_relaxed);
         return {};
     }
 
     // Potentially we can get small inconsistency while copying different statistics values. It is acceptable.
-    const auto reads = iter->second.m_reads.fetch_add(1, std::memory_order_acq_rel) + 1;
-    const auto writes = iter->second.m_writes.load(std::memory_order_acquire);
+    const auto reads = iter->second.m_reads.fetch_add(1, std::memory_order_relaxed) + 1;
+    const auto writes = iter->second.m_writes.load(std::memory_order_relaxed);
 
-    m_reads.fetch_add(1, std::memory_order_acq_rel);
+    m_reads.fetch_add(1, std::memory_order_relaxed);
 
     return { std::move(ExtendedValue{iter->second.m_value, {reads, writes}}) };
 }
@@ -55,11 +55,11 @@ void DataEngine::set(const std::string_view name, const std::string_view value)
     }
     else
     {
-        iter->second.m_writes.fetch_add(1, std::memory_order_acq_rel);
+        iter->second.m_writes.fetch_add(1, std::memory_order_relaxed);
         iter->second.m_value = value;
     }
 
-    m_writes.fetch_add(1, std::memory_order_acq_rel);
+    m_writes.fetch_add(1, std::memory_order_relaxed);
 }
 
 void DataEngine::enumerate(const std::function<EnumerateVisitorProc>& visitor) const
@@ -75,5 +75,5 @@ void DataEngine::enumerate(const std::function<EnumerateVisitorProc>& visitor) c
 DataEngine::AccessStatistics DataEngine::get_global_statistics() const
 {
     // No need in full consistency here
-    return { m_reads.load(std::memory_order_acquire), m_writes.load(std::memory_order_acquire) };
+    return { m_reads.load(std::memory_order_relaxed), m_writes.load(std::memory_order_relaxed) };
 }

DataEngine.h

@@ -46,12 +46,12 @@ class DataEngine
         // Define copy-constructor to allow easier emplacing of such values into unordered_map values
         AtomicCounter(const IntegerCounter value = 0) noexcept
         {
-            this->store(value, std::memory_order_release);
+            this->store(value, std::memory_order_relaxed);
         }
         AtomicCounter(const AtomicCounter& obj) noexcept
         {
-            const auto value = obj.load(std::memory_order_acquire);
-            this->store(value, std::memory_order_release);
+            const auto value = obj.load(std::memory_order_relaxed);
+            this->store(value, std::memory_order_relaxed);
         }
     };