- Use a rwlock as reading surpasses writing by a very large factor.

- size() does not need a lock.

1 files changed, 8 insertions, 8 deletions

diff --git a/searchlib/src/vespa/searchlib/attribute/bitvector_search_cache.h b/searchlib/src/vespa/searchlib/attribute/bitvector_search_cache.h
index 3936fb2ee67..455c27459cd 100644
--- a/searchlib/src/vespa/searchlib/attribute/bitvector_search_cache.h
+++ b/searchlib/src/vespa/searchlib/attribute/bitvector_search_cache.h
@@ -6,7 +6,8 @@
 #include <vespa/vespalib/stllike/hash_map.h>
 #include <vespa/vespalib/stllike/string.h>
 #include <memory>
-#include <mutex>
+#include <shared_mutex>
+#include <atomic>
 
 namespace search { class BitVector; }
 namespace search::attribute {
@@ -22,7 +23,6 @@ public:
     using ReadGuardSP = IDocumentMetaStoreContext::IReadGuard::SP;
 
     struct Entry {
-        using SP = std::shared_ptr<Entry>;
         // We need to keep a document meta store read guard to ensure that no lids that are cached
         // in the bit vector are re-used until the guard is released.
         ReadGuardSP dmsReadGuard;
@@ -33,18 +33,18 @@ public:
     };
 
 private:
-    using LockGuard = std::lock_guard<std::mutex>;
-    using Cache = vespalib::hash_map<vespalib::string, Entry::SP>;
+    using Cache = vespalib::hash_map<vespalib::string, std::shared_ptr<Entry>>;
 
-    mutable std::mutex _mutex;
+    mutable std::shared_mutex _mutex;
+    std::atomic<uint64_t>     _size;
     Cache _cache;
 
 public:
     BitVectorSearchCache();
     ~BitVectorSearchCache();
-    void insert(const vespalib::string &term, Entry::SP entry);
-    Entry::SP find(const vespalib::string &term) const;
-    size_t size() const;
+    void insert(const vespalib::string &term, std::shared_ptr<Entry> entry);
+    std::shared_ptr<Entry> find(const vespalib::string &term) const;
+    size_t size() const { return _size.load(std::memory_order_relaxed); }
     void clear();
 };