[lldb] Add ConstString memory usage statistics

Add statistics about the memory usage of the string pool. I'm
particularly interested in the memory used by the allocator, i.e. the
number of bytes actually used by the allocator it self as well as the
number of bytes allocated through the allocator.

Differential revision: https://reviews.llvm.org/D117914

Author: JDevlieghere

lldb/include/lldb/Target/Statistics.h

@@ -9,6 +9,7 @@
 #ifndef LLDB_TARGET_STATISTICS_H
 #define LLDB_TARGET_STATISTICS_H
 
+#include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/Stream.h"
 #include "lldb/lldb-forward.h"
 #include "llvm/Support/JSON.h"
@@ -110,6 +111,11 @@ struct ModuleStats {
   bool debug_info_index_saved_to_cache = false;
 };
 
+struct ConstStringStats {
+  llvm::json::Value ToJSON() const;
+  ConstString::MemoryStats stats = ConstString::GetMemoryStats();
+};
+
 /// A class that represents statistics for a since lldb_private::Target.
 class TargetStats {
 public:

lldb/include/lldb/Utility/ConstString.h

@@ -408,6 +408,16 @@ class ConstString {
   ///     in memory.
   static size_t StaticMemorySize();
 
+  struct MemoryStats {
+    size_t GetBytesTotal() const { return bytes_total; }
+    size_t GetBytesUsed() const { return bytes_used; }
+    size_t GetBytesUnused() const { return bytes_total - bytes_used; }
+    size_t bytes_total = 0;
+    size_t bytes_used = 0;
+  };
+
+  static MemoryStats GetMemoryStats();
+
 protected:
   template <typename T, typename Enable> friend struct ::llvm::DenseMapInfo;
   /// Only used by DenseMapInfo.

lldb/source/Target/Statistics.cpp

@@ -65,6 +65,14 @@ json::Value ModuleStats::ToJSON() const {
   return module;
 }
 
+llvm::json::Value ConstStringStats::ToJSON() const {
+  json::Object obj;
+  obj.try_emplace<int64_t>("bytesTotal", stats.GetBytesTotal());
+  obj.try_emplace<int64_t>("bytesUsed", stats.GetBytesUsed());
+  obj.try_emplace<int64_t>("bytesUnused", stats.GetBytesUnused());
+  return obj;
+}
+
 json::Value TargetStats::ToJSON(Target &target) {
   CollectStats(target);
 
@@ -212,9 +220,15 @@ llvm::json::Value DebuggerStats::ReportStatistics(Debugger &debugger,
     json_modules.emplace_back(module_stat.ToJSON());
   }
 
+  ConstStringStats const_string_stats;
+  json::Object json_memory{
+      {"strings", const_string_stats.ToJSON()},
+  };
+
   json::Object global_stats{
       {"targets", std::move(json_targets)},
       {"modules", std::move(json_modules)},
+      {"memory", std::move(json_memory)},
       {"totalSymbolTableParseTime", symtab_parse_time},
       {"totalSymbolTableIndexTime", symtab_index_time},
       {"totalSymbolTablesLoadedFromCache", symtabs_loaded},

lldb/source/Utility/ConstString.cpp

@@ -171,6 +171,17 @@ class Pool {
     return mem_size;
   }
 
+  ConstString::MemoryStats GetMemoryStats() const {
+    ConstString::MemoryStats stats;
+    for (const auto &pool : m_string_pools) {
+      llvm::sys::SmartScopedReader<false> rlock(pool.m_mutex);
+      const Allocator &alloc = pool.m_string_map.getAllocator();
+      stats.bytes_total += alloc.getTotalMemory();
+      stats.bytes_used += alloc.getBytesAllocated();
+    }
+    return stats;
+  }
+
 protected:
   uint8_t hash(const llvm::StringRef &s) const {
     uint32_t h = llvm::djbHash(s);
@@ -332,6 +343,10 @@ size_t ConstString::StaticMemorySize() {
   return StringPool().MemorySize();
 }
 
+ConstString::MemoryStats ConstString::GetMemoryStats() {
+  return StringPool().GetMemoryStats();
+}
+
 void llvm::format_provider<ConstString>::format(const ConstString &CS,
                                                 llvm::raw_ostream &OS,
                                                 llvm::StringRef Options) {

lldb/test/API/commands/statistics/basic/TestStats.py

@@ -135,6 +135,7 @@ def test_default_no_run(self):
 
         (lldb) statistics dump
         {
+          "memory" : {...},
           "modules" : [...],
           "targets" : [
             {
@@ -160,6 +161,7 @@ def test_default_no_run(self):
         target = self.createTestTarget()
         debug_stats = self.get_stats()
         debug_stat_keys = [
+            'memory',
             'modules',
             'targets',
             'totalSymbolTableParseTime',
@@ -197,6 +199,7 @@ def test_default_with_run(self):
 
         (lldb) statistics dump
         {
+          "memory" : {...},
           "modules" : [...],
           "targets" : [
                 {
@@ -227,6 +230,7 @@ def test_default_with_run(self):
                                           lldb.SBFileSpec("main.c"))
         debug_stats = self.get_stats()
         debug_stat_keys = [
+            'memory',
             'modules',
             'targets',
             'totalSymbolTableParseTime',
@@ -254,6 +258,44 @@ def test_default_with_run(self):
         self.assertGreater(stats['launchOrAttachTime'], 0.0)
         self.assertGreater(stats['targetCreateTime'], 0.0)
 
+    def test_memory(self):
+        """
+            Test "statistics dump" and the memory information.
+        """
+        exe = self.getBuildArtifact("a.out")
+        target = self.createTestTarget(file_path=exe)
+        debug_stats = self.get_stats()
+        debug_stat_keys = [
+            'memory',
+            'modules',
+            'targets',
+            'totalSymbolTableParseTime',
+            'totalSymbolTableIndexTime',
+            'totalSymbolTablesLoadedFromCache',
+            'totalSymbolTablesSavedToCache',
+            'totalDebugInfoParseTime',
+            'totalDebugInfoIndexTime',
+            'totalDebugInfoIndexLoadedFromCache',
+            'totalDebugInfoIndexSavedToCache',
+            'totalDebugInfoByteSize'
+        ]
+        self.verify_keys(debug_stats, '"debug_stats"', debug_stat_keys, None)
+
+        memory = debug_stats['memory']
+        memory_keys= [
+            'strings',
+        ]
+        self.verify_keys(memory, '"memory"', memory_keys, None)
+
+        strings = memory['strings']
+        strings_keys= [
+            'bytesTotal',
+            'bytesUsed',
+            'bytesUnused',
+        ]
+        self.verify_keys(strings, '"strings"', strings_keys, None)
+
+
     def find_module_in_metrics(self, path, stats):
         modules = stats['modules']
         for module in modules:
@@ -269,6 +311,7 @@ def test_modules(self):
         target = self.createTestTarget(file_path=exe)
         debug_stats = self.get_stats()
         debug_stat_keys = [
+            'memory',
             'modules',
             'targets',
             'totalSymbolTableParseTime',
@@ -312,6 +355,7 @@ def test_breakpoints(self):
         Output expected to be something like:
 
         {
+          "memory" : {...},
           "modules" : [...],
           "targets" : [
                 {
@@ -355,6 +399,7 @@ def test_breakpoints(self):
         self.runCmd("b a_function")
         debug_stats = self.get_stats()
         debug_stat_keys = [
+            'memory',
             'modules',
             'targets',
             'totalSymbolTableParseTime',