[clangd] Fix bugs with incorrect memory estimate report

* With the current implementation, `sizeof(std::vector<Chunk>)` is added
twice to the `Dex` memory estimate which is incorrect
* `Dex` logs memory usage estimation before `BackingDataSize` is set and
hence the log report excludes size of the external `SymbolSlab` which is
coupled with `Dex` instance

Reviewed By: ioeric

Differential Revision: https://reviews.llvm.org/D52503

llvm-svn: 343117

clang-tools-extra/clangd/index/Serialization.cpp

@@ -6,8 +6,10 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+
 #include "Serialization.h"
 #include "Index.h"
+#include "Logger.h"
 #include "RIFF.h"
 #include "Trace.h"
 #include "dex/Dex.h"
@@ -433,8 +435,12 @@ std::unique_ptr<SymbolIndex> loadIndex(llvm::StringRef SymbolFilename,
   }
 
   trace::Span Tracer("BuildIndex");
-  return UseDex ? dex::Dex::build(std::move(Symbols), URISchemes)
+  auto Index = UseDex ? dex::Dex::build(std::move(Symbols), URISchemes)
                       : MemIndex::build(std::move(Symbols), std::move(Refs));
+  vlog("Loaded {0} from {1} with estimated memory usage {2}",
+       UseDex ? "Dex" : "MemIndex", SymbolFilename,
+       Index->estimateMemoryUsage());
+  return Index;
 }
 
 } // namespace clangd

clang-tools-extra/clangd/index/dex/Dex.cpp

@@ -130,9 +130,6 @@ void Dex::buildIndex() {
   for (const auto &TokenToPostingList : TempInvertedIndex)
     InvertedIndex.insert(
         {TokenToPostingList.first, PostingList(TokenToPostingList.second)});
-
-  vlog("Built Dex with estimated memory usage {0} bytes.",
-       estimateMemoryUsage());
 }
 
 /// Constructs iterators over tokens extracted from the query and exhausts it
@@ -248,8 +245,8 @@ size_t Dex::estimateMemoryUsage() const {
   Bytes += SymbolQuality.size() * sizeof(float);
   Bytes += LookupTable.getMemorySize();
   Bytes += InvertedIndex.getMemorySize();
-  for (const auto &P : InvertedIndex)
-    Bytes += P.second.bytes();
+  for (const auto &TokenToPostingList : InvertedIndex)
+    Bytes += TokenToPostingList.second.bytes();
   return Bytes + BackingDataSize;
 }
 

clang-tools-extra/clangd/index/dex/PostingList.h

@@ -66,10 +66,8 @@ public:
   /// go through the chunks and decompress them on-the-fly when necessary.
   std::unique_ptr<Iterator> iterator() const;
 
-  /// Returns in-memory size.
-  size_t bytes() const {
-    return sizeof(Chunk) + Chunks.capacity() * sizeof(Chunk);
-  }
+  /// Returns in-memory size of external storage.
+  size_t bytes() const { return Chunks.capacity() * sizeof(Chunk); }
 
 private:
   const std::vector<Chunk> Chunks;