Add treeMemoryUsage in MemoryManager::toString (#7960)

Summary:
The number of root memory pools must be 0 during
the destruction of the `MemoryManager`, and it is nice to add
treeMemoryUsage of each pool in `MemoryManager::toString`
if there are still alive root pools, which is not normal.

Pull Request resolved: #7960

Reviewed By: tanjialiang

Differential Revision: D52023530

Pulled By: xiaoxmeng

fbshipit-source-id: bd1192c6d51b08d4be043ec4d80b355b41b91aec

velox/common/memory/Memory.cpp

@@ -86,7 +86,7 @@ MemoryManager::~MemoryManager() {
         0,
         "There are {} unexpected alive memory pools allocated by user on memory manager destruction:\n{}",
         numPools(),
-        toString());
+        toString(true));
   }
 }
 
@@ -200,18 +200,26 @@ MemoryArbitrator* MemoryManager::arbitrator() {
   return arbitrator_.get();
 }
 
-std::string MemoryManager::toString() const {
+std::string MemoryManager::toString(bool detail) const {
   std::stringstream out;
   out << "Memory Manager[capacity "
       << (capacity_ == kMaxMemory ? "UNLIMITED" : succinctBytes(capacity_))
       << " alignment " << succinctBytes(alignment_) << " usedBytes "
       << succinctBytes(getTotalBytes()) << " number of pools " << numPools()
       << "\n";
   out << "List of root pools:\n";
-  out << "\t" << defaultRoot_->name() << "\n";
+  if (detail) {
+    out << defaultRoot_->treeMemoryUsage();
+  } else {
+    out << "\t" << defaultRoot_->name() << "\n";
+  }
   std::vector<std::shared_ptr<MemoryPool>> pools = getAlivePools();
   for (const auto& pool : pools) {
-    out << "\t" << pool->name() << "\n";
+    if (detail) {
+      out << pool->treeMemoryUsage();
+    } else {
+      out << "\t" << pool->name() << "\n";
+    }
   }
   out << allocator_->toString() << "\n";
   out << arbitrator_->toString();

velox/common/memory/Memory.h

@@ -198,8 +198,10 @@ class MemoryManager {
 
   MemoryArbitrator* arbitrator();
 
-  /// Returns debug string of this memory manager.
-  std::string toString() const;
+  /// Returns debug string of this memory manager. If 'detail' is true, it
+  /// returns the detailed tree memory usage from all the top level root memory
+  /// pools.
+  std::string toString(bool detail = false) const;
 
   /// Returns the memory manger's internal default root memory pool for testing
   /// purpose.