diff --git a/lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.h b/lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.h
--- a/lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.h
+++ b/lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.h
@@ -11,6 +11,7 @@
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Threading.h"
 
 #include "Plugins/ExpressionParser/Clang/ClangASTImporter.h"
 
@@ -122,7 +123,9 @@
                      TypeIndex func_ti, CompilerType func_ct,
                      uint32_t param_count, clang::StorageClass func_storage,
                      bool is_inline, clang::DeclContext *parent);
-  void ParseAllNamespacesPlusChildrenOf(llvm::Optional<llvm::StringRef> parent);
+  void ParseNamespace(clang::DeclContext &parent);
+  void ParseAllTypes();
+  void ParseAllFunctionsAndNonLocalVars();
   void ParseDeclsForSimpleContext(clang::DeclContext &context);
   void ParseBlockChildren(PdbCompilandSymId block_id);
 
@@ -135,7 +138,8 @@
   TypeSystemClang &m_clang;
 
   ClangASTImporter m_importer;
-
+  llvm::once_flag m_parse_functions_and_non_local_vars;
+  llvm::once_flag m_parse_all_types;
   llvm::DenseMap<clang::Decl *, DeclStatus> m_decl_to_status;
   llvm::DenseMap<lldb::user_id_t, clang::Decl *> m_uid_to_decl;
   llvm::DenseMap<lldb::user_id_t, clang::QualType> m_uid_to_type;
@@ -145,6 +149,7 @@
   llvm::DenseMap<lldb::opaque_compiler_type_t,
                  llvm::SmallSet<std::pair<llvm::StringRef, CompilerType>, 8>>
       m_cxx_record_map;
+  llvm::DenseSet<clang::NamespaceDecl *> m_parsed_namespaces;
 };
 
 } // namespace npdb
diff --git a/lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.cpp b/lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.cpp
--- a/lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.cpp
+++ b/lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.cpp
@@ -21,7 +21,6 @@
 #include "lldb/Core/Module.h"
 #include "lldb/Symbol/ObjectFile.h"
 #include "lldb/Utility/LLDBAssert.h"
-
 #include "PdbUtil.h"
 #include "UdtRecordCompleter.h"
 #include "SymbolFileNativePDB.h"
@@ -1232,8 +1231,11 @@
   return llvm::isa<clang::BlockDecl>(&context);
 }
 
-void PdbAstBuilder::ParseAllNamespacesPlusChildrenOf(
-    llvm::Optional<llvm::StringRef> parent) {
+void PdbAstBuilder::ParseNamespace(clang::DeclContext &context) {
+  clang::NamespaceDecl *ns = llvm::dyn_cast<clang::NamespaceDecl>(&context);
+  if (m_parsed_namespaces.contains(ns))
+    return;
+  std::string qname = ns->getQualifiedNameAsString();
   SymbolFileNativePDB *pdb = static_cast<SymbolFileNativePDB *>(
       m_clang.GetSymbolFile()->GetBackingSymbolFile());
   PdbIndex &index = pdb->GetIndex();
@@ -1247,12 +1249,6 @@
 
     CVTagRecord tag = CVTagRecord::create(cvt);
 
-    if (!parent) {
-      clang::QualType qt = GetOrCreateType(tid);
-      CompleteType(qt);
-      continue;
-    }
-
     // Call CreateDeclInfoForType unconditionally so that the namespace info
     // gets created.  But only call CreateRecordType if the namespace name
     // matches.
@@ -1263,41 +1259,68 @@
       continue;
 
     clang::NamespaceDecl *ns = llvm::cast<clang::NamespaceDecl>(context);
-    std::string actual_ns = ns->getQualifiedNameAsString();
-    if (llvm::StringRef(actual_ns).startswith(*parent)) {
-      clang::QualType qt = GetOrCreateType(tid);
-      CompleteType(qt);
-      continue;
+    llvm::StringRef ns_name = ns->getName();
+    if (ns_name.startswith(qname)) {
+      ns_name = ns_name.drop_front(qname.size());
+      if (ns_name.startswith("::"))
+        GetOrCreateType(tid);
     }
   }
+  ParseAllFunctionsAndNonLocalVars();
+  m_parsed_namespaces.insert(ns);
+}
 
-  uint32_t module_count = index.dbi().modules().getModuleCount();
-  for (uint16_t modi = 0; modi < module_count; ++modi) {
-    CompilandIndexItem &cii = index.compilands().GetOrCreateCompiland(modi);
-    const CVSymbolArray &symbols = cii.m_debug_stream.getSymbolArray();
-    auto iter = symbols.begin();
-    while (iter != symbols.end()) {
-      PdbCompilandSymId sym_id{modi, iter.offset()};
-
-      switch (iter->kind()) {
-      case S_GPROC32:
-      case S_LPROC32:
-        GetOrCreateFunctionDecl(sym_id);
-        iter = symbols.at(getScopeEndOffset(*iter));
-        break;
-      case S_GDATA32:
-      case S_GTHREAD32:
-      case S_LDATA32:
-      case S_LTHREAD32:
-        GetOrCreateVariableDecl(PdbCompilandSymId(modi, 0), sym_id);
-        ++iter;
-        break;
-      default:
-        ++iter;
+void PdbAstBuilder::ParseAllTypes() {
+  llvm::call_once(m_parse_all_types, [this]() {
+    SymbolFileNativePDB *pdb = static_cast<SymbolFileNativePDB *>(
+        m_clang.GetSymbolFile()->GetBackingSymbolFile());
+    PdbIndex &index = pdb->GetIndex();
+    TypeIndex ti{index.tpi().TypeIndexBegin()};
+    for (const CVType &cvt : index.tpi().typeArray()) {
+      PdbTypeSymId tid{ti};
+      ++ti;
+
+      if (!IsTagRecord(cvt))
         continue;
+
+      GetOrCreateType(tid);
+    }
+  });
+}
+
+void PdbAstBuilder::ParseAllFunctionsAndNonLocalVars() {
+  llvm::call_once(m_parse_functions_and_non_local_vars, [this]() {
+    SymbolFileNativePDB *pdb = static_cast<SymbolFileNativePDB *>(
+        m_clang.GetSymbolFile()->GetBackingSymbolFile());
+    PdbIndex &index = pdb->GetIndex();
+    uint32_t module_count = index.dbi().modules().getModuleCount();
+    for (uint16_t modi = 0; modi < module_count; ++modi) {
+      CompilandIndexItem &cii = index.compilands().GetOrCreateCompiland(modi);
+      const CVSymbolArray &symbols = cii.m_debug_stream.getSymbolArray();
+      auto iter = symbols.begin();
+      while (iter != symbols.end()) {
+        PdbCompilandSymId sym_id{modi, iter.offset()};
+
+        switch (iter->kind()) {
+        case S_GPROC32:
+        case S_LPROC32:
+          GetOrCreateFunctionDecl(sym_id);
+          iter = symbols.at(getScopeEndOffset(*iter));
+          break;
+        case S_GDATA32:
+        case S_GTHREAD32:
+        case S_LDATA32:
+        case S_LTHREAD32:
+          GetOrCreateVariableDecl(PdbCompilandSymId(modi, 0), sym_id);
+          ++iter;
+          break;
+        default:
+          ++iter;
+          continue;
+        }
       }
     }
-  }
+  });
 }
 
 static CVSymbolArray skipFunctionParameters(clang::Decl &decl,
@@ -1384,14 +1407,13 @@
   // work (such as parsing the items that appear within the namespaces) at the
   // same time.
   if (context.isTranslationUnit()) {
-    ParseAllNamespacesPlusChildrenOf(llvm::None);
+    ParseAllTypes();
+    ParseAllFunctionsAndNonLocalVars();
     return;
   }
 
   if (context.isNamespace()) {
-    clang::NamespaceDecl &ns = *llvm::dyn_cast<clang::NamespaceDecl>(&context);
-    std::string qname = ns.getQualifiedNameAsString();
-    ParseAllNamespacesPlusChildrenOf(llvm::StringRef{qname});
+    ParseNamespace(context);
     return;
   }