diff --git a/clang-tools-extra/clangd/ClangdLSPServer.h b/clang-tools-extra/clangd/ClangdLSPServer.h
--- a/clang-tools-extra/clangd/ClangdLSPServer.h
+++ b/clang-tools-extra/clangd/ClangdLSPServer.h
@@ -24,6 +24,7 @@
 #include "llvm/ADT/StringSet.h"
 #include "llvm/Support/JSON.h"
 #include <chrono>
+#include <cstddef>
 #include <memory>
 
 namespace clang {
@@ -141,6 +142,9 @@
   void onSemanticTokens(const SemanticTokensParams &, Callback<SemanticTokens>);
   void onSemanticTokensDelta(const SemanticTokensDeltaParams &,
                              Callback<SemanticTokensOrDelta>);
+  /// This is a clangd extension. It invokes a showMessage with current
+  /// profiling info.
+  void onDumpMemoryTree(const NoParams &, Callback<std::nullptr_t>);
 
   std::vector<Fix> getFixes(StringRef File, const clangd::Diagnostic &D);
 
diff --git a/clang-tools-extra/clangd/ClangdLSPServer.cpp b/clang-tools-extra/clangd/ClangdLSPServer.cpp
--- a/clang-tools-extra/clangd/ClangdLSPServer.cpp
+++ b/clang-tools-extra/clangd/ClangdLSPServer.cpp
@@ -36,8 +36,11 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SHA1.h"
 #include "llvm/Support/ScopedPrinter.h"
+#include "llvm/Support/raw_ostream.h"
 #include <chrono>
 #include <cstddef>
+#include <cstdint>
+#include <functional>
 #include <memory>
 #include <mutex>
 #include <string>
@@ -1383,6 +1386,38 @@
       });
 }
 
+void ClangdLSPServer::onDumpMemoryTree(const NoParams &,
+                                       Callback<std::nullptr_t> Reply) {
+  llvm::BumpPtrAllocator Alloc;
+  MemoryTree MT(&Alloc);
+  profile(MT);
+
+  std::function<size_t(llvm::StringRef, const MemoryTree &, llvm::raw_ostream &,
+                       size_t)>
+      DumpTree = [&](llvm::StringRef Key, const MemoryTree &MT,
+                     llvm::raw_ostream &OS, size_t Indent) {
+        size_t Total = MT.self();
+        std::string ChildText;
+        llvm::raw_string_ostream ChildStream(ChildText);
+        for (const auto &Entry : MT.children()) {
+          ChildStream << '\n';
+          Total +=
+              DumpTree(Entry.first, Entry.getSecond(), ChildStream, Indent + 2);
+        }
+        OS << std::string(Indent, ' ') << Key << ": " << Total << " bytes"
+           << ChildStream.str();
+        return Total;
+      };
+
+  ShowMessageParams Msg;
+  llvm::raw_string_ostream Str(Msg.message);
+  DumpTree("clangd_lsp_server", MT, Str, 0);
+  Str.flush();
+
+  notify("window/showMessage", std::move(Msg));
+  Reply(nullptr);
+}
+
 ClangdLSPServer::ClangdLSPServer(class Transport &Transp,
                                  const ThreadsafeFS &TFS,
                                  const ClangdLSPServer::Options &Opts)
@@ -1425,6 +1460,7 @@
   MsgHandler->bind("textDocument/documentLink", &ClangdLSPServer::onDocumentLink);
   MsgHandler->bind("textDocument/semanticTokens/full", &ClangdLSPServer::onSemanticTokens);
   MsgHandler->bind("textDocument/semanticTokens/full/delta", &ClangdLSPServer::onSemanticTokensDelta);
+  MsgHandler->bind("$/dumpMemoryTree", &ClangdLSPServer::onDumpMemoryTree);
   if (Opts.FoldingRanges)
     MsgHandler->bind("textDocument/foldingRange", &ClangdLSPServer::onFoldingRange);
   // clang-format on
diff --git a/clang-tools-extra/clangd/test/memory_tree.test b/clang-tools-extra/clangd/test/memory_tree.test
new file mode 100644
--- /dev/null
+++ b/clang-tools-extra/clangd/test/memory_tree.test
@@ -0,0 +1,33 @@
+# RUN: clangd -lit-test < %s | FileCheck -strict-whitespace %s
+{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
+---
+{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"test:///main.cpp","languageId":"cpp","version":1,"text":"void func() {}"}}}
+---
+{"jsonrpc":"2.0","id":1,"method":"$/dumpMemoryTree","params":{}}
+# CHECK:      "method": "window/showMessage",
+# CHECK-NEXT:   "params": {
+# CHECK-NEXT:     "message": "
+# CHECK-SAME:       clangd_lsp_server: {{[0-9]+}} bytes\n
+# CHECK-SAME:         clangd_server: {{[0-9]+}} bytes\n
+# CHECK-SAME:           tuscheduler: {{[0-9]+}} bytes\n
+# CHECK-SAME:             /clangd-test/main.cpp: {{[0-9]+}} bytes\n
+# CHECK-SAME:               ast: {{[0-9]+}} bytes\n
+# CHECK-SAME:               preamble: {{[0-9]+}} bytes\n
+# CHECK-SAME:           dynamic_index: {{[0-9]+}} bytes\n
+# CHECK-SAME:             preamble: {{[0-9]+}} bytes\n
+# CHECK-SAME:               symbols: {{[0-9]+}} bytes\n
+# CHECK-SAME:               index: {{[0-9]+}} bytes\n
+# CHECK-SAME:             main_file: {{[0-9]+}} bytes\n
+# CHECK-SAME:               symbols: {{[0-9]+}} bytes\n
+# CHECK-SAME:                 /clangd-test/main.cpp: {{[0-9]+}} bytes\n
+# CHECK-SAME:                   relations: {{[0-9]+}} bytes\n
+# CHECK-SAME:                   references: {{[0-9]+}} bytes\n
+# CHECK-SAME:                   symbols: {{[0-9]+}} bytes\n
+# CHECK-SAME:               index: {{[0-9]+}} bytes"
+# CHECK-NEXT:    "type": 3
+# CHECK-NEXT:  }
+---
+{"jsonrpc":"2.0","id":3,"method":"shutdown"}
+---
+{"jsonrpc":"2.0","method":"exit"}
+