From 14b7b40a82003689e2ac197995b8731584ac8168 Mon Sep 17 00:00:00 2001
From: Matthew Parkinson <mattpark@microsoft.com>
Date: Thu, 5 May 2022 11:09:37 +0100
Subject: [PATCH] Add a Stats combiner to make code cleaner.

---
 src/snmalloc/backend/backend.h            | 30 ++++++++---------------
 src/snmalloc/backend_helpers/statsrange.h | 18 ++++++++++++++
 2 files changed, 28 insertions(+), 20 deletions(-)

diff --git a/src/snmalloc/backend/backend.h b/src/snmalloc/backend/backend.h
index be498f4..db380fc 100644
--- a/src/snmalloc/backend/backend.h
+++ b/src/snmalloc/backend/backend.h
@@ -134,22 +134,22 @@ namespace snmalloc
     // Source for object allocations
     using StatsObject = StatsRange<CommitRange<CentralObectRange, PAL>>;
     using ObjectRange = LargeBuddyRange<StatsObject, 21, 21, Pagemap>;
-    using StatsR = StatsObject;
 
-    using StatsRMeta = StatsRange<CommitRange<CentralMetaRange, PAL>>;
+    using StatsMeta = StatsRange<CommitRange<CentralMetaRange, PAL>>;
 
     using MetaRange = SmallBuddyRange<
-      LargeBuddyRange<StatsRMeta, 21 - 6, bits::BITS - 1, Pagemap>>;
+      LargeBuddyRange<StatsMeta, 21 - 6, bits::BITS - 1, Pagemap>>;
     // Create global range that can service small meta-data requests.
     // Don't want to add this to the CentralMetaRange to move Commit outside the
     // lock on the common case.
-    using GlobalMetaRange = GlobalRange<SmallBuddyRange<StatsRMeta>>;
+    using GlobalMetaRange = GlobalRange<SmallBuddyRange<StatsMeta>>;
+    using Stats = StatsCombiner<StatsObject, StatsMeta>;
 #else
     // Source for object allocations and metadata
     // No separation between the two
-    using StatsR = StatsRange<GlobalR>;
+    using Stats = StatsRange<GlobalR>;
     using ObjectRange = SmallBuddyRange<
-      LargeBuddyRange<CommitRange<StatsR, PAL>, 21, 21, Pagemap>>;
+      LargeBuddyRange<CommitRange<Stats, PAL>, 21, 21, Pagemap>>;
     using GlobalMetaRange = GlobalRange<ObjectRange>;
 #endif
 
@@ -321,24 +321,14 @@ namespace snmalloc
 
     static size_t get_current_usage()
     {
-      StatsR stats_state;
-      auto result = stats_state.get_current_usage();
-#ifdef SNMALLOC_PROTECT_METADATA
-      StatsRMeta stats_state_meta;
-      result += stats_state_meta.get_current_usage();
-#endif
-      return result;
+      Stats stats_state;
+      return stats_state.get_current_usage();
     }
 
     static size_t get_peak_usage()
     {
-      StatsR stats_state;
-      auto result = stats_state.get_peak_usage();
-#ifdef SNMALLOC_PROTECT_METADATA
-      StatsRMeta stats_state_meta;
-      result += stats_state_meta.get_peak_usage();
-#endif
-      return result;
+      Stats stats_state;
+      return stats_state.get_peak_usage();
     }
   };
 } // namespace snmalloc
diff --git a/src/snmalloc/backend_helpers/statsrange.h b/src/snmalloc/backend_helpers/statsrange.h
index da874b2..98a06ae 100644
--- a/src/snmalloc/backend_helpers/statsrange.h
+++ b/src/snmalloc/backend_helpers/statsrange.h
@@ -54,4 +54,22 @@ namespace snmalloc
       return peak_usage.load();
     }
   };
+
+  template<typename StatsR1, typename StatsR2>
+  class StatsCombiner
+  {
+    StatsR1 r1{};
+    StatsR2 r2{};
+
+  public:
+    size_t get_current_usage()
+    {
+      return r1.get_current_usage() + r2.get_current_usage();
+    }
+
+    size_t get_peak_usage()
+    {
+      return r1.get_peak_usage() + r2.get_peak_usage();
+    }
+  };
 } // namespace snmalloc