Index: clang-tools-extra/clangd/benchmarks/IndexBenchmark.cpp
===================================================================
--- clang-tools-extra/clangd/benchmarks/IndexBenchmark.cpp
+++ clang-tools-extra/clangd/benchmarks/IndexBenchmark.cpp
@@ -66,6 +66,27 @@
   return Requests;
 }
 
+// This is not a *real* benchmark: it shows size of built MemIndex (in bytes).
+// Same for the next "benchmark".
+// FIXME(kbobyrev): Should this be separated into the BackingMemorySize
+// (underlying SymbolSlab size) and Symbol Index (MemIndex/Dex) overhead?
+static void MemSize(benchmark::State &State) {
+  const auto Mem = buildMem();
+  for (auto _ : State)
+    // Divide size of Mem by 1000 so that it will be correctly displayed in the
+    // benchmark report (possible options for time units are ms, ns and us).
+    State.SetIterationTime(/*double Seconds=*/Mem->estimateMemoryUsage() /
+                           1000);
+}
+BENCHMARK(MemSize)->UseManualTime()->Unit(benchmark::kMillisecond);
+
+static void DexSize(benchmark::State &State) {
+  const auto Dex = buildDex();
+  for (auto _ : State)
+    State.SetIterationTime(Dex->estimateMemoryUsage() / 1000);
+}
+BENCHMARK(DexSize)->UseManualTime()->Unit(benchmark::kMillisecond);
+
 static void MemQueries(benchmark::State &State) {
   const auto Mem = buildMem();
   const auto Requests = extractQueriesFromLogs();