Index: clang-tools-extra/clangd/benchmarks/IndexBenchmark.cpp
===================================================================
--- clang-tools-extra/clangd/benchmarks/IndexBenchmark.cpp
+++ clang-tools-extra/clangd/benchmarks/IndexBenchmark.cpp
@@ -12,6 +12,7 @@
 #include "benchmark/benchmark.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Regex.h"
 #include <fstream>
@@ -33,6 +34,25 @@
   return loadIndex(IndexFilename, {}, true);
 }
 
+SymbolSlab loadSlab() {
+  auto Buffer = llvm::MemoryBuffer::getFile(IndexFilename);
+  if (!Buffer) {
+    llvm::errs() << "Can't open " << IndexFilename << '\n';
+    exit(1);
+  }
+
+  auto Slab = readIndexFile((*Buffer)->getBuffer());
+  if (!Slab) {
+    llvm::errs() << llvm::toString(Slab.takeError()) << '\n';
+    exit(1);
+  } else if (!Slab->Symbols) {
+    llvm::errs() << "Couldn't read symbol slab from the index file: "
+                 << IndexFilename << '\n';
+    exit(1);
+  }
+  return std::move(*Slab->Symbols);
+}
+
 // Reads JSON array of serialized FuzzyFindRequest's from user-provided file.
 std::vector<FuzzyFindRequest> extractQueriesFromLogs() {
   std::ifstream InputStream(RequestsFilename);
@@ -73,7 +93,7 @@
     for (const auto &Request : Requests)
       Mem->fuzzyFind(Request, [](const Symbol &S) {});
 }
-BENCHMARK(MemQueries);
+BENCHMARK(MemQueries)->Unit(benchmark::kMillisecond);
 
 static void DexQueries(benchmark::State &State) {
   const auto Dex = buildDex();
@@ -82,15 +102,72 @@
     for (const auto &Request : Requests)
       Dex->fuzzyFind(Request, [](const Symbol &S) {});
 }
-BENCHMARK(DexQueries);
+BENCHMARK(DexQueries)->Unit(benchmark::kMillisecond);
+
+// This is not a *real* benchmark: it shows size of built MemIndex (in bytes).
+// Same for the next "benchmark".
+// FIXME(kbobyrev): Track memory usage caused by different index parts:
+// SymbolSlab and RefSlabs, InverseIndex, PostingLists of different types for
+// Dex, etc.
+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() /
+                           1000.0);
+  State.SetLabel("This tracks in-memory size of MemIndex (SymbolSlab + Index "
+                 "overhead) in bytes");
+}
+BENCHMARK(MemSize)
+    ->UseManualTime()
+    ->Unit(benchmark::kMillisecond)
+    ->Iterations(1);
+
+static void DexSize(benchmark::State &State) {
+  const auto Dex = buildDex();
+
+  for (auto _ : State)
+    State.SetIterationTime(Dex->estimateMemoryUsage() / 1000.0);
+  State.SetLabel("This tracks in-memory size of Dex (SymbolSlab + Index "
+                 "overhead) in bytes");
+}
+BENCHMARK(DexSize)
+    ->UseManualTime()
+    ->Unit(benchmark::kMillisecond)
+    ->Iterations(1);
+
+static void DexOverhead(benchmark::State &State) {
+  const auto Slab = loadSlab();
+  const auto Dex = buildDex();
+  for (auto _ : State)
+    State.SetIterationTime((Dex->estimateMemoryUsage() - Slab.bytes()) /
+                           1000.0);
+  State.SetLabel("This tracks in-memory size of Dex Index overhead (and "
+                 "excludes underlying SymbolSlab size) in bytes");
+}
+BENCHMARK(DexOverhead)
+    ->UseManualTime()
+    ->Unit(benchmark::kMillisecond)
+    ->Iterations(1);
+
+static void SymbolSlabLoading(benchmark::State &State) {
+  for (auto _ : State)
+    benchmark::DoNotOptimize(loadSlab());
+}
+BENCHMARK(SymbolSlabLoading)->Unit(benchmark::kMillisecond);
+
+static void DexBuild(benchmark::State &State) {
+  auto Slab = loadSlab();
+  for (auto _ : State)
+    benchmark::DoNotOptimize(dex::Dex::build(std::move(Slab), {}));
+}
+BENCHMARK(DexBuild)->Unit(benchmark::kMillisecond);
 
 } // namespace
 } // namespace clangd
 } // namespace clang
 
-// FIXME(kbobyrev): Add index building time benchmarks.
-// FIXME(kbobyrev): Add memory consumption "benchmarks" by manually measuring
-// in-memory index size and reporting it as time.
 // FIXME(kbobyrev): Create a logger wrapper to suppress debugging info printer.
 int main(int argc, char *argv[]) {
   if (argc < 3) {