From 49bd43e685e0e66753aa9ba1094a790ebfdeebf9 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Sun, 5 Feb 2023 18:46:20 -0800
Subject: [PATCH] ircd::util: Optimize instance_map w/ allocator::node.

---
 include/ircd/util/instance_map.h | 76 +++++++++++++++++++++++---------
 ircd/resource.cc                 | 11 ++++-
 2 files changed, 64 insertions(+), 23 deletions(-)

diff --git a/include/ircd/util/instance_map.h b/include/ircd/util/instance_map.h
index 8e5ee7f7f..3c01354f0 100644
--- a/include/ircd/util/instance_map.h
+++ b/include/ircd/util/instance_map.h
@@ -26,13 +26,24 @@ template<class K,
          class C>
 struct ircd::util::instance_map
 {
-	static std::map<K, T *, C> map;
+	using value_type = std::pair<const K, T *>;
+	using allocator_state_type = ircd::allocator::node<value_type>;
+	using allocator_scope = typename allocator_state_type::scope;
+	using allocator_type = typename allocator_state_type::allocator;
+	using map_type = std::map<K, T *, C, allocator_type>;
+	using node_type = std::pair<typename map_type::node_type, value_type>;
+	using iterator_type = typename map_type::iterator;
+	using const_iterator_type = typename map_type::const_iterator;
+
+	static allocator_state_type allocator;
+	static map_type map;
 
   protected:
-	typename decltype(map)::iterator it;
+	node_type node;
+	iterator_type it;
 
 	template<class Key>
-	instance_map(const typename decltype(map)::const_iterator &hint, Key&&);
+	instance_map(const const_iterator_type &hint, Key&&);
 
 	template<class Key>
 	instance_map(Key&&);
@@ -51,6 +62,11 @@ template<class Key>
 inline
 ircd::util::instance_map<K, T, C>::instance_map(Key&& key)
 {
+	const allocator_scope alloca
+	{
+		map, this->node
+	};
+
 	auto [it, ok]
 	{
 		map.emplace(std::forward<Key>(key), static_cast<T *>(this))
@@ -70,9 +86,14 @@ template<class K,
          class C>
 template<class Key>
 inline
-ircd::util::instance_map<K, T, C>::instance_map(const typename decltype(map)::const_iterator &hint,
+ircd::util::instance_map<K, T, C>::instance_map(const const_iterator_type &hint,
                                                 Key&& key)
 {
+	const allocator_scope alloca
+	{
+		map, this->node
+	};
+
 	auto [it, ok]
 	{
 		map.emplace_hint(hint, std::forward<Key>(key), static_cast<T *>(this))
@@ -93,16 +114,15 @@ template<class K,
 inline
 ircd::util::instance_map<K, T, C>::instance_map(instance_map &&other)
 noexcept
-:it
 {
-	std::move(other.it)
-}
-{
-	if(it != end(map))
+	const allocator_scope alloca
 	{
-		it->second = static_cast<T *>(this);
-		other.it = end(map);
-	}
+		map, this->node
+	};
+
+	it = likely(other.it != end(map))?
+		map.emplace_hint(other.it, other.it->first, static_cast<T *>(this)):
+		end(map);
 }
 
 template<class K,
@@ -110,13 +130,16 @@ template<class K,
          class C>
 inline
 ircd::util::instance_map<K, T, C>::instance_map(const instance_map &other)
-:it
 {
-	other.it != end(map)?
+	const allocator_scope alloca
+	{
+		map, this->node
+	};
+
+	it = likely(other.it != end(map))?
 		map.emplace_hint(other.it, other.it->first, static_cast<T *>(this)):
-		end(map)
+		end(map);
 }
-{}
 
 template<class K,
          class T,
@@ -126,11 +149,16 @@ ircd::util::instance_map<K, T, C>::operator=(instance_map &&other)
 noexcept
 {
 	this->~instance_map();
-	it = std::move(other.it);
-	if(it != end(map))
-		it->second = static_cast<T *>(this);
 
-	other.it = end(map);
+	const allocator_scope alloca
+	{
+		map, this->node
+	};
+
+	it = likely(other.it != end(map))?
+		map.emplace_hint(other.it, other.it->first, static_cast<T *>(this)):
+		end(map);
+
 	return *this;
 }
 
@@ -141,7 +169,13 @@ inline ircd::util::instance_map<K, T, C> &
 ircd::util::instance_map<K, T, C>::operator=(const instance_map &other)
 {
 	this->~instance_map();
-	it = other.it != end(map)?
+
+	const allocator_scope alloca
+	{
+		map, this->node
+	};
+
+	it = likely(other.it != end(map))?
 		map.emplace_hint(other.it, other.it->first, static_cast<T *>(this)):
 		end(map);
 
diff --git a/ircd/resource.cc b/ircd/resource.cc
index 8020e416e..9e46e1bff 100644
--- a/ircd/resource.cc
+++ b/ircd/resource.cc
@@ -15,10 +15,17 @@ ircd::resource::log
 };
 
 template<>
-decltype(ircd::util::instance_map<ircd::string_view, ircd::resource, ircd::iless>::map)
-ircd::util::instance_map<ircd::string_view, ircd::resource, ircd::iless>::map
+decltype(ircd::resource::allocator)
+ircd::util::instance_map<ircd::string_view, ircd::resource, ircd::iless>::allocator
 {};
 
+template<>
+decltype(ircd::resource::map)
+ircd::util::instance_map<ircd::string_view, ircd::resource, ircd::iless>::map
+{
+	allocator
+};
+
 ircd::resource &
 ircd::resource::find(const string_view &path_)
 {